* Re: [PATCH 6/9] Add a general, global device notification watch list [ver #5]
From: Greg Kroah-Hartman @ 2019-07-05 8:44 UTC (permalink / raw)
To: David Howells
Cc: viro, Casey Schaufler, Stephen Smalley, nicolas.dichtel, raven,
Christian Brauner, keyrings, linux-usb, linux-security-module,
linux-fsdevel, linux-api, linux-block, linux-kernel
In-Reply-To: <12946.1562313857@warthog.procyon.org.uk>
On Fri, Jul 05, 2019 at 09:04:17AM +0100, David Howells wrote:
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
>
> > Hm, good point, but there should be some way to test this to verify it
> > works. Maybe for the other types of events?
>
> Keyrings is the simplest. keyutils's testsuite will handle that. I'm trying
> to work out if I can simply make every macro in there that does a modification
> perform a watch automatically to make sure the appropriate events happen.
That should be good enough to test the basic functionality. After this
gets merged I'll see if I can come up with a way to test the USB
stuff...
thanks,
greg k-h
^ permalink raw reply
* Re: [PATCH 6/9] Add a general, global device notification watch list [ver #5]
From: Alan Stern @ 2019-07-05 14:40 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: David Howells, viro, Casey Schaufler, Stephen Smalley,
nicolas.dichtel, raven, Christian Brauner, keyrings, linux-usb,
linux-security-module, linux-fsdevel, linux-api, linux-block,
linux-kernel
In-Reply-To: <20190705084459.GA2579@kroah.com>
On Fri, 5 Jul 2019, Greg Kroah-Hartman wrote:
> On Fri, Jul 05, 2019 at 09:04:17AM +0100, David Howells wrote:
> > Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> >
> > > Hm, good point, but there should be some way to test this to verify it
> > > works. Maybe for the other types of events?
> >
> > Keyrings is the simplest. keyutils's testsuite will handle that. I'm trying
> > to work out if I can simply make every macro in there that does a modification
> > perform a watch automatically to make sure the appropriate events happen.
>
> That should be good enough to test the basic functionality. After this
> gets merged I'll see if I can come up with a way to test the USB
> stuff...
You can create USB connect and disconnect events programmatically by
using dummy-hcd with gadget-zero. Turning off the port's POWER feature
will cause a disconnect, and turning it back on will cause a connect.
Alan Stern
^ permalink raw reply
* [PATCH v9 00/10] namei: openat2(2) path resolution restrictions
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Eric Biederman, Andy Lutomirski, Jann Horn,
Christian Brauner, David Drysdale, Tycho Andersen, Kees Cook,
Linus Torvalds, containers, linux-fsdevel, linux-api,
Andrew Morton, Alexei Starovoitov, Chanho Min, Oleg Nesterov,
Aleksa Sarai, linux-alpha, linux-arch, linux-arm-kernel,
linux-ia64, linux-kernel
Patch changelog:
v9:
* Replace resolveat(2) with openat2(2). [Linus]
* Output a warning to dmesg if may_open_magiclink() is violated.
* Add an openat2(O_CREAT) testcase.
v8:
* Default to O_CLOEXEC to match other new fd-creation syscalls
(users can always disable O_CLOEXEC afterwards). [Christian]
* Implement magic-link restrictions based on their mode. This is
done through a series of masks and is designed to avoid breaking
users -- most users don't have chained O_PATH fd re-opens.
* Add O_EMPTYPATH which allows for fd re-opening without needing
procfs. This would help some users of fd re-opening, and with the
changes to magic-link permissions we now have the right semantics
for such a flag.
* Add selftests for resolveat(2), O_EMPTYPATH, and the magic-link
mode semantics.
v7:
* Remove execveat(2) support for these flags since it might
result in some pretty hairy security issues with setuid binaries.
There are other avenues we can go down to solve the issues with
CVE-2019-5736. [Jann]
* Reserve an additional bit in resolveat(2) for the eXecute access
mode if we end up implementing it.
v6:
* Drop O_* flags API to the new LOOKUP_ path scoping bits and
instead introduce resolveat(2) as an alternative method of
obtaining an O_PATH. The justification for this is included in
patch 6 (though switching back to O_* flags is trivial).
v5:
* In response to CVE-2019-5736 (one of the vectors showed that
open(2)+fexec(3) cannot be used to scope binfmt_script's implicit
open_exec()), AT_* flags have been re-added and are now piped
through to binfmt_script (and other binfmt_* that use open_exec)
but are only supported for execveat(2) for now.
v4:
* Remove AT_* flag reservations, as they require more discussion.
* Switch to path_is_under() over __d_path() for breakout checking.
* Make O_XDEV no longer block openat("/tmp", "/", O_XDEV) -- dirfd
is now ignored for absolute paths to match other flags.
* Improve the dirfd_path_init() refactor and move it to a separate
commit.
* Remove reference to Linux-capsicum.
* Switch "proclink" name to magic-link.
v3: [resend]
v2:
* Made ".." resolution with AT_THIS_ROOT and AT_BENEATH safe(r) with
some semi-aggressive __d_path checking (see patch 3).
* Disallowed "proclinks" with AT_THIS_ROOT and AT_BENEATH, in the
hopes they can be re-enabled once safe.
* Removed the selftests as they will be reimplemented as xfstests.
* Removed stat(2) support, since you can already get it through
O_PATH and fstatat(2).
The need for some sort of control over VFS's path resolution (to avoid
malicious paths resulting in inadvertent breakouts) has been a very
long-standing desire of many userspace applications. This patchset is a
revival of Al Viro's old AT_NO_JUMPS[1,2] patchset (which was a variant
of David Drysdale's O_BENEATH patchset[3] which was a spin-off of the
Capsicum project[4]) with a few additions and changes made based on the
previous discussion within [5] as well as others I felt were useful.
In line with the conclusions of the original discussion of AT_NO_JUMPS,
the flag has been split up into separate flags. However, instead of
being an openat(2) flag it is provided through a new syscall openat2(2)
which provides an alternative way to get an O_PATH file descriptor (the
reasoning for doing this is included in patch 6). The following new
LOOKUP_ flags are added:
* LOOKUP_XDEV blocks all mountpoint crossings (upwards, downwards, or
through absolute links). Absolute pathnames alone in openat(2) do
not trigger this.
* LOOKUP_NO_MAGICLINKS blocks resolution through /proc/$pid/fd-style
links. This is done by blocking the usage of nd_jump_link() during
resolution in a filesystem. The term "magic-links" is used to match
with the only reference to these links in Documentation/, but I'm
happy to change the name.
It should be noted that this is different to the scope of
~LOOKUP_FOLLOW in that it applies to all path components. However,
you can do openat2(NO_FOLLOW|NO_MAGICLINKS) on a magic-link and it
will *not* fail (assuming that no parent component was a
magic-link), and you will have an fd for the magic-link.
* LOOKUP_BENEATH disallows escapes to outside the starting dirfd's
tree, using techniques such as ".." or absolute links. Absolute
paths in openat(2) are also disallowed. Conceptually this flag is to
ensure you "stay below" a certain point in the filesystem tree --
but this requires some additional to protect against various races
that would allow escape using "..".
Currently LOOKUP_BENEATH implies LOOKUP_NO_MAGICLINKS, because it
can trivially beam you around the filesystem (breaking the
protection). In future, there might be similar safety checks done as
in LOOKUP_IN_ROOT, but that requires more discussion.
In addition, two new flags are added that expand on the above ideas:
* LOOKUP_NO_SYMLINKS does what it says on the tin. No symlink
resolution is allowed at all, including magic-links. Just as with
LOOKUP_NO_MAGICLINKS this can still be used with NOFOLLOW to open an
fd for the symlink as long as no parent path had a symlink
component.
* LOOKUP_IN_ROOT is an extension of LOOKUP_BENEATH that, rather than
blocking attempts to move past the root, forces all such movements
to be scoped to the starting point. This provides chroot(2)-like
protection but without the cost of a chroot(2) for each filesystem
operation, as well as being safe against race attacks that chroot(2)
is not.
If a race is detected (as with LOOKUP_BENEATH) then an error is
generated, and similar to LOOKUP_BENEATH it is not permitted to cross
magic-links with LOOKUP_IN_ROOT.
The primary need for this is from container runtimes, which
currently need to do symlink scoping in userspace[6] when opening
paths in a potentially malicious container. There is a long list of
CVEs that could have bene mitigated by having O_THISROOT (such as
CVE-2017-1002101, CVE-2017-1002102, CVE-2018-15664, and
CVE-2019-5736, just to name a few).
And further, several semantics of file descriptor "re-opening" are now
changed to prevent attacks like CVE-2019-5736 by restricting how
magic-links can be resolved (based on their mode). This required some
other changes to the semantics of the modes of O_PATH file descriptor's
associated /proc/self/fd magic-links. openat2(2) has the ability to
further restrict re-opening of its own O_PATH fds, so that users can
make even better use of this feature.
Finally, O_EMPTYPATH was added so that users can do /proc/self/fd-style
re-opening without depending on procfs. The new restricted semantics for
magic-links are applied here too.
In order to make all of the above more usable, I'm working on
libpathrs[7] which is a C-friendly library for safe path resolution. It
features a userspace-emulated backend if the kernel doesn't support
openat2(2). Hopefully we can get userspace to switch to using it, and
thus get openat2(2) support for free once it's ready.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Christian Brauner <christian@brauner.io>
Cc: David Drysdale <drysdale@google.com>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <containers@lists.linux-foundation.org>
Cc: <linux-fsdevel@vger.kernel.org>
Cc: <linux-api@vger.kernel.org>
[1]: https://lwn.net/Articles/721443/
[2]: https://lore.kernel.org/patchwork/patch/784221/
[3]: https://lwn.net/Articles/619151/
[4]: https://lwn.net/Articles/603929/
[5]: https://lwn.net/Articles/723057/
[6]: https://github.com/cyphar/filepath-securejoin
[7]: https://github.com/openSUSE/libpathrs
Aleksa Sarai (10):
namei: obey trailing magic-link DAC permissions
procfs: switch magic-link modes to be more sane
open: O_EMPTYPATH: procfs-less file descriptor re-opening
namei: split out nd->dfd handling to dirfd_path_init
namei: O_BENEATH-style path resolution flags
namei: LOOKUP_IN_ROOT: chroot-like path resolution
namei: aggressively check for nd->root escape on ".." resolution
open: openat2(2) syscall
kselftest: save-and-restore errno to allow for %m formatting
selftests: add openat2(2) selftests
arch/alpha/kernel/syscalls/syscall.tbl | 1 +
arch/arm/tools/syscall.tbl | 1 +
arch/arm64/include/asm/unistd.h | 2 +-
arch/arm64/include/asm/unistd32.h | 2 +
arch/ia64/kernel/syscalls/syscall.tbl | 1 +
arch/m68k/kernel/syscalls/syscall.tbl | 1 +
arch/microblaze/kernel/syscalls/syscall.tbl | 1 +
arch/mips/kernel/syscalls/syscall_n32.tbl | 1 +
arch/mips/kernel/syscalls/syscall_n64.tbl | 1 +
arch/mips/kernel/syscalls/syscall_o32.tbl | 1 +
arch/parisc/kernel/syscalls/syscall.tbl | 1 +
arch/powerpc/kernel/syscalls/syscall.tbl | 1 +
arch/s390/kernel/syscalls/syscall.tbl | 1 +
arch/sh/kernel/syscalls/syscall.tbl | 1 +
arch/sparc/kernel/syscalls/syscall.tbl | 1 +
arch/x86/entry/syscalls/syscall_32.tbl | 1 +
arch/x86/entry/syscalls/syscall_64.tbl | 1 +
arch/xtensa/kernel/syscalls/syscall.tbl | 1 +
fs/fcntl.c | 2 +-
fs/internal.h | 1 +
fs/namei.c | 333 ++++++++++++---
fs/open.c | 140 +++++--
fs/proc/base.c | 20 +-
fs/proc/fd.c | 23 +-
fs/proc/namespaces.c | 2 +-
include/linux/fcntl.h | 17 +-
include/linux/fs.h | 8 +-
include/linux/namei.h | 8 +
include/linux/syscalls.h | 14 +-
include/uapi/asm-generic/fcntl.h | 5 +
include/uapi/asm-generic/unistd.h | 5 +-
include/uapi/linux/fcntl.h | 38 ++
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/kselftest.h | 15 +
tools/testing/selftests/memfd/memfd_test.c | 7 +-
tools/testing/selftests/openat2/.gitignore | 1 +
tools/testing/selftests/openat2/Makefile | 12 +
tools/testing/selftests/openat2/helpers.c | 162 +++++++
tools/testing/selftests/openat2/helpers.h | 114 +++++
.../testing/selftests/openat2/linkmode_test.c | 325 ++++++++++++++
.../selftests/openat2/rename_attack_test.c | 124 ++++++
.../testing/selftests/openat2/resolve_test.c | 395 ++++++++++++++++++
42 files changed, 1667 insertions(+), 125 deletions(-)
create mode 100644 tools/testing/selftests/openat2/.gitignore
create mode 100644 tools/testing/selftests/openat2/Makefile
create mode 100644 tools/testing/selftests/openat2/helpers.c
create mode 100644 tools/testing/selftests/openat2/helpers.h
create mode 100644 tools/testing/selftests/openat2/linkmode_test.c
create mode 100644 tools/testing/selftests/openat2/rename_attack_test.c
create mode 100644 tools/testing/selftests/openat2/resolve_test.c
--
2.22.0
^ permalink raw reply
* [PATCH v9 01/10] namei: obey trailing magic-link DAC permissions
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Andy Lutomirski, Christian Brauner, Eric Biederman,
Andrew Morton, Alexei Starovoitov, Kees Cook, Jann Horn,
Tycho Andersen, David Drysdale, Chanho Min, Oleg Nesterov,
Aleksa Sarai, Linus Torvalds, containers, linux-alpha, linux-api,
linux-arch, linux-arm-kernel, linux-fsdevel, linux-ia64,
linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
The ability for userspace to "re-open" file descriptors through
/proc/self/fd has been a very useful tool for all sorts of usecases
(container runtimes are one common example). However, the current
interface for doing this has resulted in some pretty subtle security
holes. Userspace can re-open a file descriptor with more permissions
than the original, which can result in cases such as /proc/$pid/exe
being re-opened O_RDWR at a later date even though (by definition)
/proc/$pid/exe cannot be opened for writing. When combined with O_PATH
the results can get even more confusing.
We cannot block this outright. Aside from userspace already depending on
it, it's a useful feature which can actually increase the security of
userspace. For instance, LXC keeps an O_PATH of the container's
/dev/pts/ptmx that gets re-opened to create new ptys and then uses
TIOCGPTPEER to get the slave end. This allows for pty allocation without
resolving paths inside an (untrusted) container's rootfs. There isn't a
trivial way of doing this that is as straight-forward and safe as O_PATH
re-opening.
Instead we have to restrict it in such a way that it doesn't break
(good) users but does block potential attackers. The solution applied in
this patch is to restrict *re-opening* (not resolution through)
magic-links by requiring that mode of the link be obeyed. Normal
symlinks have modes of a+rwx but magic-links have other modes. These
magic-link modes were historically ignored during path resolution, but
they've now been re-purposed for more useful ends.
It is also necessary to define semantics for the mode of an O_PATH
descriptor, since re-opening a magic-link through an O_PATH needs to be
just as restricted as the corresponding magic-link otherwise the above
protection can be bypassed. There are two distinct cases:
1. The target is a regular file (not a magic-link). Userspace depends
on being able to re-open the O_PATH of a regular file, so we must
define the mode to be a+rwx.
2. The target is a magic-link. In this case, we simply copy the mode of
the magic-link. This results in an O_PATH of a magic-link
effectively acting as a no-op in terms of how much re-opening
privileges a process has.
CAP_DAC_OVERRIDE can be used to override all of these restrictions, but
we only permit &init_userns's capabilities to affect these semantics.
The reason for this is that there isn't a clear way to track what
user_ns is the original owner of a given O_PATH chain -- thus an
unprivileged user could create a new userns and O_PATH the file
descriptor, owning it. All signs would indicate that the user really
does have CAP_DAC_OVERRIDE over the new descriptor and the protection
would be bypassed. We thus opt for the more conservative approach.
I have run this patch on several machines for several days. So far, the
only processes which have hit this case ("loadkeys" and "kbd_mode" from
the kbd package[1]) gracefully handle the permission error and do not
cause any user-visible problems. In order to give users a heads-up, a
warning is given whenever may_open_magiclink() refuses access.
[1]: http://git.altlinux.org/people/legion/packages/kbd.git
Co-developed-by: Andy Lutomirski <luto@kernel.org>
Co-developed-by: Christian Brauner <christian@brauner.io>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
fs/internal.h | 1 +
fs/namei.c | 103 +++++++++++++++++++++++++++++++++++++++++++--
fs/open.c | 3 +-
fs/proc/fd.c | 23 +++++++++-
include/linux/fs.h | 4 ++
5 files changed, 127 insertions(+), 7 deletions(-)
diff --git a/fs/internal.h b/fs/internal.h
index a48ef81be37d..12847f502f49 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -119,6 +119,7 @@ struct open_flags {
int acc_mode;
int intent;
int lookup_flags;
+ fmode_t opath_mask;
};
extern struct file *do_filp_open(int dfd, struct filename *pathname,
const struct open_flags *op);
diff --git a/fs/namei.c b/fs/namei.c
index 20831c2fbb34..4ec6168762db 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -506,6 +506,8 @@ struct nameidata {
struct inode *link_inode;
unsigned root_seq;
int dfd;
+ fmode_t opath_mask;
+ int acc_mode; /* op.acc_mode */
} __randomize_layout;
static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
@@ -514,7 +516,14 @@ static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
p->stack = p->internal;
p->dfd = dfd;
p->name = name;
- p->total_link_count = old ? old->total_link_count : 0;
+ p->total_link_count = 0;
+ p->acc_mode = 0;
+ p->opath_mask = FMODE_PATH_READ | FMODE_PATH_WRITE;
+ if (old) {
+ p->total_link_count = old->total_link_count;
+ p->acc_mode = old->acc_mode;
+ p->opath_mask = old->opath_mask;
+ }
p->saved = old;
current->nameidata = p;
}
@@ -1042,8 +1051,52 @@ static int may_create_in_sticky(struct dentry * const dir,
return 0;
}
+/**
+ * may_reopen_magiclink - Check permissions for opening a trailing magic-link
+ * @opath_mask: the O_PATH mask of the magic-link
+ * @acc_mode: ACC_MODE which the user is attempting
+ *
+ * We block magic-link re-opening if the @opath_mask is more strict than the
+ * @acc_mode being requested, unless the user is capable(CAP_DAC_OVERRIDE).
+ *
+ * Returns 0 if successful, -ve on error.
+ */
+static int may_open_magiclink(fmode_t opath_mask, int acc_mode)
+{
+ /*
+ * We only allow for init_userns to be able to override magic-links.
+ * This is done to avoid cases where an unprivileged userns could take
+ * an O_PATH of the fd, resulting in it being very unclear whether
+ * CAP_DAC_OVERRIDE should work on the new O_PATH fd (given that it
+ * pipes through to the underlying file).
+ */
+ if (capable(CAP_DAC_OVERRIDE))
+ return 0;
+
+ if ((acc_mode & MAY_READ) &&
+ !(opath_mask & (FMODE_READ | FMODE_PATH_READ)))
+ goto err;
+ if ((acc_mode & MAY_WRITE) &&
+ !(opath_mask & (FMODE_WRITE | FMODE_PATH_WRITE)))
+ goto err;
+
+ return 0;
+
+err:
+ pr_warn_ratelimited("%s[%d]: magic-link re-open blocked (acc_mode=%s%s%s, opath_mask=%s%s%s%s)",
+ current->comm, task_pid_nr(current),
+ (acc_mode & MAY_READ) ? "r": "",
+ (acc_mode & MAY_WRITE) ? "w": "",
+ (acc_mode & MAY_EXEC) ? "x": "",
+ (opath_mask & FMODE_READ) ? "R" : "",
+ (opath_mask & FMODE_PATH_READ) ? "r" : "",
+ (opath_mask & FMODE_WRITE) ? "W" : "",
+ (opath_mask & FMODE_PATH_WRITE) ? "w" : "");
+ return -EACCES;
+}
+
static __always_inline
-const char *get_link(struct nameidata *nd)
+const char *get_link(struct nameidata *nd, bool trailing)
{
struct saved *last = nd->stack + nd->depth - 1;
struct dentry *dentry = last->link.dentry;
@@ -1081,6 +1134,44 @@ const char *get_link(struct nameidata *nd)
} else {
res = get(dentry, inode, &last->done);
}
+ /* If we just jumped it was because of a magic-link. */
+ if (unlikely(nd->flags & LOOKUP_JUMPED)) {
+ /*
+ * For trailing_symlink we check whether the symlink's
+ * mode allows us to do what we want through acc_mode.
+ * In addition, we need to stash away what the link
+ * mode is in case we are about to O_PATH this
+ * magic-link.
+ *
+ * This is only done for magic-links, as a security
+ * measure to prevent users from being able to re-open
+ * files with additional permissions or similar tricks
+ * through procfs. This is not strictly POSIX-friendly,
+ * but technically neither are magic-links.
+ */
+ if (trailing) {
+ fmode_t opath_mask = 0;
+
+ /*
+ * Figure out the O_PATH mask. Rather than
+ * using acl_permission_check, we check whether
+ * any of the rw bits are set in the mode.
+ */
+ if (inode->i_mode & S_IRUGO)
+ opath_mask |= FMODE_PATH_READ;
+ if (inode->i_mode & S_IWUGO)
+ opath_mask |= FMODE_PATH_WRITE;
+
+ /*
+ * Is the new opath_mask more restrictive than
+ * the acc_mode being requested?
+ */
+ error = may_open_magiclink(opath_mask, nd->acc_mode);
+ if (error)
+ return ERR_PTR(error);
+ nd->opath_mask &= opath_mask;
+ }
+ }
if (IS_ERR_OR_NULL(res))
return res;
}
@@ -2142,7 +2233,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
return err;
if (err) {
- const char *s = get_link(nd);
+ const char *s = get_link(nd, false);
if (IS_ERR(s))
return PTR_ERR(s);
@@ -2258,7 +2349,7 @@ static const char *trailing_symlink(struct nameidata *nd)
return ERR_PTR(error);
nd->flags |= LOOKUP_PARENT;
nd->stack[0].name = NULL;
- s = get_link(nd);
+ s = get_link(nd, true);
return s ? s : "";
}
@@ -3508,6 +3599,7 @@ static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
if (!error) {
audit_inode(nd->name, path.dentry, 0);
error = vfs_open(&path, file);
+ file->f_mode |= nd->opath_mask;
path_put(&path);
}
return error;
@@ -3519,6 +3611,9 @@ static struct file *path_openat(struct nameidata *nd,
struct file *file;
int error;
+ nd->acc_mode = op->acc_mode;
+ nd->opath_mask = op->opath_mask;
+
file = alloc_empty_file(op->open_flag, current_cred());
if (IS_ERR(file))
return file;
diff --git a/fs/open.c b/fs/open.c
index b5b80469b93d..ab20eae39df7 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -982,8 +982,9 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
acc_mode |= MAY_APPEND;
op->acc_mode = acc_mode;
-
op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
+ /* For O_PATH backwards-compatibility we default to an all-set mask. */
+ op->opath_mask = FMODE_PATH_READ | FMODE_PATH_WRITE;
if (flags & O_CREAT) {
op->intent |= LOOKUP_CREATE;
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 81882a13212d..9b7d8becb002 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -104,11 +104,30 @@ static void tid_fd_update_inode(struct task_struct *task, struct inode *inode,
task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
if (S_ISLNK(inode->i_mode)) {
+ /*
+ * Always set +x (depending on the fmode type), since there
+ * currently aren't FMODE_PATH_EXEC restrictions and there is
+ * no O_MAYEXEC yet. This might change in the future, in which
+ * case we will restrict +x.
+ */
unsigned i_mode = S_IFLNK;
+ if (f_mode & FMODE_PATH)
+ i_mode |= S_IXGRP;
+ else
+ i_mode |= S_IXUSR;
+ /*
+ * Construct the mode bits based on the open-mode. The u+rwx
+ * bits are for "ordinary" open modes while g+rwx are for
+ * O_PATH modes.
+ */
if (f_mode & FMODE_READ)
- i_mode |= S_IRUSR | S_IXUSR;
+ i_mode |= S_IRUSR;
if (f_mode & FMODE_WRITE)
- i_mode |= S_IWUSR | S_IXUSR;
+ i_mode |= S_IWUSR;
+ if (f_mode & FMODE_PATH_READ)
+ i_mode |= S_IRGRP;
+ if (f_mode & FMODE_PATH_WRITE)
+ i_mode |= S_IWGRP;
inode->i_mode = i_mode;
}
security_task_to_inode(task, inode);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f7fdfe93e25d..f7df213405ea 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -173,6 +173,10 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
/* File does not contribute to nr_files count */
#define FMODE_NOACCOUNT ((__force fmode_t)0x20000000)
+/* File is an O_PATH descriptor which can be upgraded to (read, write). */
+#define FMODE_PATH_READ ((__force fmode_t)0x40000000)
+#define FMODE_PATH_WRITE ((__force fmode_t)0x80000000)
+
/*
* Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector
* that indicates that they should check the contents of the iovec are
--
2.22.0
^ permalink raw reply related
* [PATCH v9 02/10] procfs: switch magic-link modes to be more sane
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Eric Biederman, Andy Lutomirski, Andrew Morton,
Alexei Starovoitov, Kees Cook, Jann Horn, Christian Brauner,
Tycho Andersen, David Drysdale, Chanho Min, Oleg Nesterov,
Aleksa Sarai, Linus Torvalds, containers, linux-alpha, linux-api,
linux-arch, linux-arm-kernel, linux-fsdevel, linux-ia64,
linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
Now that magic-link modes are obeyed for file re-opening purposes, some
of the pre-existing magic-link modes need to be adjusted to be more
semantically correct.
The most blatant example of this is /proc/self/exe, which had a mode of
a+rwx even though tautologically the file could never be opened for
writing (because it is the current->mm of a live process).
With the new O_PATH restrictions, changing the default mode of these
magic-links allows us to avoid delayed-access attacks such as we saw in
CVE-2019-5736.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
fs/proc/base.c | 20 ++++++++++----------
fs/proc/namespaces.c | 2 +-
2 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 255f6754c70d..82c06c21e69d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -133,9 +133,9 @@ struct pid_entry {
#define DIR(NAME, MODE, iops, fops) \
NOD(NAME, (S_IFDIR|(MODE)), &iops, &fops, {} )
-#define LNK(NAME, get_link) \
- NOD(NAME, (S_IFLNK|S_IRWXUGO), \
- &proc_pid_link_inode_operations, NULL, \
+#define LNK(NAME, MODE, get_link) \
+ NOD(NAME, (S_IFLNK|(MODE)), \
+ &proc_pid_link_inode_operations, NULL, \
{ .proc_get_link = get_link } )
#define REG(NAME, MODE, fops) \
NOD(NAME, (S_IFREG|(MODE)), NULL, &fops, {})
@@ -2995,9 +2995,9 @@ static const struct pid_entry tgid_base_stuff[] = {
REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
#endif
REG("mem", S_IRUSR|S_IWUSR, proc_mem_operations),
- LNK("cwd", proc_cwd_link),
- LNK("root", proc_root_link),
- LNK("exe", proc_exe_link),
+ LNK("cwd", S_IRWXUGO, proc_cwd_link),
+ LNK("root", S_IRWXUGO, proc_root_link),
+ LNK("exe", S_IRUGO|S_IXUGO, proc_exe_link),
REG("mounts", S_IRUGO, proc_mounts_operations),
REG("mountinfo", S_IRUGO, proc_mountinfo_operations),
REG("mountstats", S_IRUSR, proc_mountstats_operations),
@@ -3393,11 +3393,11 @@ static const struct pid_entry tid_base_stuff[] = {
REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
#endif
REG("mem", S_IRUSR|S_IWUSR, proc_mem_operations),
- LNK("cwd", proc_cwd_link),
- LNK("root", proc_root_link),
- LNK("exe", proc_exe_link),
+ LNK("cwd", S_IRWXUGO, proc_cwd_link),
+ LNK("root", S_IRWXUGO, proc_root_link),
+ LNK("exe", S_IRUGO|S_IXUGO, proc_exe_link),
REG("mounts", S_IRUGO, proc_mounts_operations),
- REG("mountinfo", S_IRUGO, proc_mountinfo_operations),
+ REG("mountinfo", S_IRUGO, proc_mountinfo_operations),
#ifdef CONFIG_PROC_PAGE_MONITOR
REG("clear_refs", S_IWUSR, proc_clear_refs_operations),
REG("smaps", S_IRUGO, proc_pid_smaps_operations),
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index dd2b35f78b09..cd1e130913f7 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -94,7 +94,7 @@ static struct dentry *proc_ns_instantiate(struct dentry *dentry,
struct inode *inode;
struct proc_inode *ei;
- inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK | S_IRWXUGO);
+ inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK | S_IRUGO);
if (!inode)
return ERR_PTR(-ENOENT);
--
2.22.0
^ permalink raw reply related
* [PATCH v9 03/10] open: O_EMPTYPATH: procfs-less file descriptor re-opening
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Eric Biederman, Andy Lutomirski, Andrew Morton,
Alexei Starovoitov, Kees Cook, Jann Horn, Christian Brauner,
Tycho Andersen, David Drysdale, Chanho Min, Oleg Nesterov,
Aleksa Sarai, Linus Torvalds, containers, linux-alpha, linux-api,
linux-arch, linux-arm-kernel, linux-fsdevel, linux-ia64,
linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
Userspace has made use of /proc/self/fd very liberally to allow for
descriptors to be re-opened. There are a wide variety of uses for this
feature, but it has always required constructing a pathname and could
not be done without procfs mounted. The obvious solution for this is to
extend openat(2) to have an AT_EMPTY_PATH-equivalent -- O_EMPTYPATH.
Now that descriptor re-opening has been made safe through the new
magic-link resolution restrictions, we can replicate these restrictions
for O_EMPTYPATH. In particular, we only allow "upgrading" the file
descriptor if the corresponding FMODE_PATH_* bit is set (or the
FMODE_{READ,WRITE} cases for non-O_PATH file descriptors).
When doing openat(O_EMPTYPATH|O_PATH), O_PATH takes precedence and
O_EMPTYPATH is ignored. Very few users ever have a need to O_PATH
re-open an existing file descriptor, and so accommodating them at the
expense of further complicating O_PATH makes little sense. Ultimately,
if users ask for this we can always add RESOLVE_EMPTY_PATH to
resolveat(2) in the future.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
fs/fcntl.c | 2 +-
fs/namei.c | 27 +++++++++++++++++++++++++++
fs/open.c | 7 ++++++-
include/linux/fcntl.h | 2 +-
include/uapi/asm-generic/fcntl.h | 5 +++++
5 files changed, 40 insertions(+), 3 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 3d40771e8e7c..4cf05a2fd162 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -1031,7 +1031,7 @@ static int __init fcntl_init(void)
* Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
* is defined as O_NONBLOCK on some platforms and not on others.
*/
- BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ !=
+ BUILD_BUG_ON(22 - 1 /* for O_RDONLY being 0 */ !=
HWEIGHT32(
(VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) |
__FMODE_EXEC | __FMODE_NONOTIFY));
diff --git a/fs/namei.c b/fs/namei.c
index 4ec6168762db..4895717d2760 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3605,6 +3605,31 @@ static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
return error;
}
+static int do_o_emptypath(struct nameidata *nd, struct file *newfile)
+{
+ int error;
+ struct fd f;
+
+ /* We don't support AT_FDCWD since O_PATH cannot be set here. */
+ f = fdget_raw(nd->dfd);
+ if (!f.file)
+ return -EBADF;
+
+ /* Update opath_mask as though we went through trailing_symlink(). */
+ if (!(f.file->f_mode & (FMODE_READ | FMODE_PATH_READ)))
+ nd->opath_mask &= ~FMODE_PATH_READ;
+ if (!(f.file->f_mode & (FMODE_WRITE | FMODE_PATH_WRITE)))
+ nd->opath_mask &= ~FMODE_PATH_WRITE;
+
+ /* Obey the same restrictions as magic-links. */
+ error = may_open_magiclink(f.file->f_mode, nd->acc_mode);
+ if (!error)
+ error = vfs_open(&f.file->f_path, newfile);
+
+ fdput(f);
+ return error;
+}
+
static struct file *path_openat(struct nameidata *nd,
const struct open_flags *op, unsigned flags)
{
@@ -3620,6 +3645,8 @@ static struct file *path_openat(struct nameidata *nd,
if (unlikely(file->f_flags & __O_TMPFILE)) {
error = do_tmpfile(nd, flags, op, file);
+ } else if (unlikely(file->f_flags & O_EMPTYPATH)) {
+ error = do_o_emptypath(nd, file);
} else if (unlikely(file->f_flags & O_PATH)) {
error = do_o_path(nd, flags, file);
} else {
diff --git a/fs/open.c b/fs/open.c
index ab20eae39df7..bdca45528524 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -996,6 +996,8 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
lookup_flags |= LOOKUP_DIRECTORY;
if (!(flags & O_NOFOLLOW))
lookup_flags |= LOOKUP_FOLLOW;
+ if (flags & O_EMPTYPATH)
+ lookup_flags |= LOOKUP_EMPTY;
op->lookup_flags = lookup_flags;
return 0;
}
@@ -1057,14 +1059,17 @@ long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
{
struct open_flags op;
int fd = build_open_flags(flags, mode, &op);
+ int empty = 0;
struct filename *tmp;
if (fd)
return fd;
- tmp = getname(filename);
+ tmp = getname_flags(filename, op.lookup_flags, &empty);
if (IS_ERR(tmp))
return PTR_ERR(tmp);
+ if (!empty)
+ op.open_flag &= ~O_EMPTYPATH;
fd = get_unused_fd_flags(flags);
if (fd >= 0) {
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index d019df946cb2..2868ae6c8fc1 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -9,7 +9,7 @@
(O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | \
O_APPEND | O_NDELAY | O_NONBLOCK | O_NDELAY | __O_SYNC | O_DSYNC | \
FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \
- O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE)
+ O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE | O_EMPTYPATH)
#ifndef force_o_largefile
#define force_o_largefile() (!IS_ENABLED(CONFIG_ARCH_32BIT_OFF_T))
diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h
index 9dc0bf0c5a6e..307f7c414a51 100644
--- a/include/uapi/asm-generic/fcntl.h
+++ b/include/uapi/asm-generic/fcntl.h
@@ -89,6 +89,11 @@
#define __O_TMPFILE 020000000
#endif
+#ifndef O_EMPTYPATH
+#define O_EMPTYPATH 040000000
+#endif
+
+
/* a horrid kludge trying to make sure that this will fail on old kernels */
#define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
#define O_TMPFILE_MASK (__O_TMPFILE | O_DIRECTORY | O_CREAT)
--
2.22.0
^ permalink raw reply related
* [PATCH v9 04/10] namei: split out nd->dfd handling to dirfd_path_init
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Eric Biederman, Andy Lutomirski, Andrew Morton,
Alexei Starovoitov, Kees Cook, Jann Horn, Christian Brauner,
Tycho Andersen, David Drysdale, Chanho Min, Oleg Nesterov,
Aleksa Sarai, Linus Torvalds, containers, linux-alpha, linux-api,
linux-arch, linux-arm-kernel, linux-fsdevel, linux-ia64,
linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
Previously, path_init's handling of *at(dfd, ...) was only done once,
but with LOOKUP_BENEATH (and LOOKUP_IN_ROOT) we have to parse the
initial nd->path at different times (before or after absolute path
handling) depending on whether we have been asked to scope resolution
within a root.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
fs/namei.c | 103 ++++++++++++++++++++++++++++++-----------------------
1 file changed, 59 insertions(+), 44 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 4895717d2760..b490bcf855f8 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2257,9 +2257,59 @@ static int link_path_walk(const char *name, struct nameidata *nd)
}
}
+/*
+ * Configure nd->path based on the nd->dfd. This is only used as part of
+ * path_init().
+ */
+static inline int dirfd_path_init(struct nameidata *nd)
+{
+ if (nd->dfd == AT_FDCWD) {
+ if (nd->flags & LOOKUP_RCU) {
+ struct fs_struct *fs = current->fs;
+ unsigned seq;
+
+ do {
+ seq = read_seqcount_begin(&fs->seq);
+ nd->path = fs->pwd;
+ nd->inode = nd->path.dentry->d_inode;
+ nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+ } while (read_seqcount_retry(&fs->seq, seq));
+ } else {
+ get_fs_pwd(current->fs, &nd->path);
+ nd->inode = nd->path.dentry->d_inode;
+ }
+ } else {
+ /* Caller must check execute permissions on the starting path component */
+ struct fd f = fdget_raw(nd->dfd);
+ struct dentry *dentry;
+
+ if (!f.file)
+ return -EBADF;
+
+ dentry = f.file->f_path.dentry;
+
+ if (*nd->name->name && unlikely(!d_can_lookup(dentry))) {
+ fdput(f);
+ return -ENOTDIR;
+ }
+
+ nd->path = f.file->f_path;
+ if (nd->flags & LOOKUP_RCU) {
+ nd->inode = nd->path.dentry->d_inode;
+ nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
+ } else {
+ path_get(&nd->path);
+ nd->inode = nd->path.dentry->d_inode;
+ }
+ fdput(f);
+ }
+ return 0;
+}
+
/* must be paired with terminate_walk() */
static const char *path_init(struct nameidata *nd, unsigned flags)
{
+ int error;
const char *s = nd->name->name;
if (!*s)
@@ -2293,52 +2343,17 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->m_seq = read_seqbegin(&mount_lock);
if (*s == '/') {
- set_root(nd);
- if (likely(!nd_jump_root(nd)))
- return s;
- return ERR_PTR(-ECHILD);
- } else if (nd->dfd == AT_FDCWD) {
- if (flags & LOOKUP_RCU) {
- struct fs_struct *fs = current->fs;
- unsigned seq;
-
- do {
- seq = read_seqcount_begin(&fs->seq);
- nd->path = fs->pwd;
- nd->inode = nd->path.dentry->d_inode;
- nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
- } while (read_seqcount_retry(&fs->seq, seq));
- } else {
- get_fs_pwd(current->fs, &nd->path);
- nd->inode = nd->path.dentry->d_inode;
- }
- return s;
- } else {
- /* Caller must check execute permissions on the starting path component */
- struct fd f = fdget_raw(nd->dfd);
- struct dentry *dentry;
-
- if (!f.file)
- return ERR_PTR(-EBADF);
-
- dentry = f.file->f_path.dentry;
-
- if (*s && unlikely(!d_can_lookup(dentry))) {
- fdput(f);
- return ERR_PTR(-ENOTDIR);
- }
-
- nd->path = f.file->f_path;
- if (flags & LOOKUP_RCU) {
- nd->inode = nd->path.dentry->d_inode;
- nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
- } else {
- path_get(&nd->path);
- nd->inode = nd->path.dentry->d_inode;
- }
- fdput(f);
+ if (likely(!nd->root.mnt))
+ set_root(nd);
+ error = nd_jump_root(nd);
+ if (unlikely(error))
+ s = ERR_PTR(error);
return s;
}
+ error = dirfd_path_init(nd);
+ if (unlikely(error))
+ return ERR_PTR(error);
+ return s;
}
static const char *trailing_symlink(struct nameidata *nd)
--
2.22.0
^ permalink raw reply related
* [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Christian Brauner, David Drysdale, Andy Lutomirski,
Linus Torvalds, Eric Biederman, Andrew Morton, Alexei Starovoitov,
Kees Cook, Jann Horn, Tycho Andersen, Chanho Min, Oleg Nesterov,
Aleksa Sarai, containers, linux-alpha, linux-api, linux-arch,
linux-arm-kernel, linux-fsdevel, linux-ia64, linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
Add the following flags to allow various restrictions on path
resolution (these affect the *entire* resolution, rather than just the
final path component -- as is the case with most other AT_* flags).
The primary justification for these flags is to allow for programs to be
far more strict about how they want path resolution to handle symlinks,
mountpoint crossings, and paths that escape the dirfd (through an
absolute path or ".." shenanigans).
This is of particular concern to container runtimes that want to be very
careful about malicious root filesystems that a container's init might
have screwed around with (and there is no real way to protect against
this in userspace if you consider potential races against a malicious
container's init). More classical applications (which have their own
potentially buggy userspace path sanitisation code) include web
servers, archive extraction tools, network file servers, and so on.
These flags are exposed to userspace in a later patchset.
* LOOKUP_XDEV: Disallow mount-point crossing (both *down* into one, or
*up* from one). The primary "scoping" use is to blocking resolution
that crosses a bind-mount, which has a similar property to a symlink
(in the way that it allows for escape from the starting-point). Since
it is not possible to differentiate bind-mounts However since
bind-mounting requires privileges (in ways symlinks don't) this has
been split from LOOKUP_BENEATH. The naming is based on "find -xdev" as
well as -EXDEV (though find(1) doesn't walk upwards, the semantics
seem obvious).
* LOOKUP_NO_MAGICLINKS: Disallows ->get_link "symlink" jumping. This is
a very specific restriction, and it exists because /proc/$pid/fd/...
"symlinks" allow for access outside nd->root and pose risk to
container runtimes that don't want to be tricked into accessing a host
path (but do want to allow no-funny-business symlink resolution).
* LOOKUP_NO_SYMLINKS: Disallows symlink jumping *of any kind*. Implies
LOOKUP_NO_MAGICLINKS (obviously).
* LOOKUP_BENEATH: Disallow "escapes" from the starting point of the
filesystem tree during resolution (you must stay "beneath" the
starting point at all times). Currently this is done by disallowing
".." and absolute paths (either in the given path or found during
symlink resolution) entirely, as well as all magic-link jumping.
The wholesale banning of ".." is because it is currently not safe to
allow ".." resolution (races can cause the path to be moved outside of
the root -- this is conceptually similar to historical chroot(2)
escape attacks). Future patches in this series will address this, and
will re-enable ".." resolution once it is safe. With those patches,
".." resolution will only be allowed if it remains in the root
throughout resolution (such as "a/../b" not "a/../../outside/b").
The banning of magic-link jumping is done because it is not clear
whether semantically they should be allowed -- while some magic-links
are safe there are many that can cause escapes (and once a
resolution is outside of the root, O_BENEATH will no longer detect
it). Future patches may re-enable magic-link jumping when such jumps
would remain inside the root.
The LOOKUP_NO_*LINK flags return -ELOOP if path resolution would
violates their requirement, while the others all return -EXDEV.
This is a refresh of Al's AT_NO_JUMPS patchset[1] (which was a variation
on David Drysdale's O_BENEATH patchset[2], which in turn was based on
the Capsicum project[3]). Input from Linus and Andy in the AT_NO_JUMPS
thread[4] determined most of the API changes made in this refresh.
[1]: https://lwn.net/Articles/721443/
[2]: https://lwn.net/Articles/619151/
[3]: https://lwn.net/Articles/603929/
[4]: https://lwn.net/Articles/723057/
Cc: Christian Brauner <christian@brauner.io>
Suggested-by: David Drysdale <drysdale@google.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Suggested-by: Andy Lutomirski <luto@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
fs/namei.c | 74 ++++++++++++++++++++++++++++++++++++-------
include/linux/namei.h | 7 ++++
2 files changed, 70 insertions(+), 11 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index b490bcf855f8..9c3ed597466b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -852,6 +852,13 @@ static inline void path_to_nameidata(const struct path *path,
static int nd_jump_root(struct nameidata *nd)
{
+ if (unlikely(nd->flags & LOOKUP_BENEATH))
+ return -EXDEV;
+ if (unlikely(nd->flags & LOOKUP_XDEV)) {
+ /* Absolute path arguments to path_init() are allowed. */
+ if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt)
+ return -EXDEV;
+ }
if (nd->flags & LOOKUP_RCU) {
struct dentry *d;
nd->path = nd->root;
@@ -1104,6 +1111,9 @@ const char *get_link(struct nameidata *nd, bool trailing)
int error;
const char *res;
+ if (unlikely(nd->flags & LOOKUP_NO_SYMLINKS))
+ return ERR_PTR(-ELOOP);
+
if (!(nd->flags & LOOKUP_RCU)) {
touch_atime(&last->link);
cond_resched();
@@ -1136,6 +1146,11 @@ const char *get_link(struct nameidata *nd, bool trailing)
}
/* If we just jumped it was because of a magic-link. */
if (unlikely(nd->flags & LOOKUP_JUMPED)) {
+ if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS))
+ return ERR_PTR(-ELOOP);
+ /* Not currently safe. */
+ if (unlikely(nd->flags & LOOKUP_BENEATH))
+ return ERR_PTR(-EXDEV);
/*
* For trailing_symlink we check whether the symlink's
* mode allows us to do what we want through acc_mode.
@@ -1178,8 +1193,9 @@ const char *get_link(struct nameidata *nd, bool trailing)
if (*res == '/') {
if (!nd->root.mnt)
set_root(nd);
- if (unlikely(nd_jump_root(nd)))
- return ERR_PTR(-ECHILD);
+ error = nd_jump_root(nd);
+ if (unlikely(error))
+ return ERR_PTR(error);
while (unlikely(*++res == '/'))
;
}
@@ -1360,12 +1376,16 @@ static int follow_managed(struct path *path, struct nameidata *nd)
break;
}
- if (need_mntput && path->mnt == mnt)
- mntput(path->mnt);
+ if (need_mntput) {
+ if (path->mnt == mnt)
+ mntput(path->mnt);
+ if (unlikely(nd->flags & LOOKUP_XDEV))
+ ret = -EXDEV;
+ else
+ nd->flags |= LOOKUP_JUMPED;
+ }
if (ret == -EISDIR || !ret)
ret = 1;
- if (need_mntput)
- nd->flags |= LOOKUP_JUMPED;
if (unlikely(ret < 0))
path_put_conditional(path, nd);
return ret;
@@ -1422,6 +1442,8 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
mounted = __lookup_mnt(path->mnt, path->dentry);
if (!mounted)
break;
+ if (unlikely(nd->flags & LOOKUP_XDEV))
+ return false;
path->mnt = &mounted->mnt;
path->dentry = mounted->mnt.mnt_root;
nd->flags |= LOOKUP_JUMPED;
@@ -1442,8 +1464,11 @@ static int follow_dotdot_rcu(struct nameidata *nd)
struct inode *inode = nd->inode;
while (1) {
- if (path_equal(&nd->path, &nd->root))
+ if (path_equal(&nd->path, &nd->root)) {
+ if (unlikely(nd->flags & LOOKUP_BENEATH))
+ return -EXDEV;
break;
+ }
if (nd->path.dentry != nd->path.mnt->mnt_root) {
struct dentry *old = nd->path.dentry;
struct dentry *parent = old->d_parent;
@@ -1468,6 +1493,8 @@ static int follow_dotdot_rcu(struct nameidata *nd)
return -ECHILD;
if (&mparent->mnt == nd->path.mnt)
break;
+ if (unlikely(nd->flags & LOOKUP_XDEV))
+ return -EXDEV;
/* we know that mountpoint was pinned */
nd->path.dentry = mountpoint;
nd->path.mnt = &mparent->mnt;
@@ -1482,6 +1509,8 @@ static int follow_dotdot_rcu(struct nameidata *nd)
return -ECHILD;
if (!mounted)
break;
+ if (unlikely(nd->flags & LOOKUP_XDEV))
+ return -EXDEV;
nd->path.mnt = &mounted->mnt;
nd->path.dentry = mounted->mnt.mnt_root;
inode = nd->path.dentry->d_inode;
@@ -1570,8 +1599,11 @@ static int path_parent_directory(struct path *path)
static int follow_dotdot(struct nameidata *nd)
{
while(1) {
- if (path_equal(&nd->path, &nd->root))
+ if (path_equal(&nd->path, &nd->root)) {
+ if (unlikely(nd->flags & LOOKUP_BENEATH))
+ return -EXDEV;
break;
+ }
if (nd->path.dentry != nd->path.mnt->mnt_root) {
int ret = path_parent_directory(&nd->path);
if (ret)
@@ -1580,6 +1612,8 @@ static int follow_dotdot(struct nameidata *nd)
}
if (!follow_up(&nd->path))
break;
+ if (unlikely(nd->flags & LOOKUP_XDEV))
+ return -EXDEV;
}
follow_mount(&nd->path);
nd->inode = nd->path.dentry->d_inode;
@@ -1794,6 +1828,13 @@ static inline int may_lookup(struct nameidata *nd)
static inline int handle_dots(struct nameidata *nd, int type)
{
if (type == LAST_DOTDOT) {
+ /*
+ * LOOKUP_BENEATH resolving ".." is not currently safe -- races can
+ * cause our parent to have moved outside of the root and us to skip
+ * over it.
+ */
+ if (unlikely(nd->flags & LOOKUP_BENEATH))
+ return -EXDEV;
if (!nd->root.mnt)
set_root(nd);
if (nd->flags & LOOKUP_RCU) {
@@ -2342,6 +2383,15 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->path.dentry = NULL;
nd->m_seq = read_seqbegin(&mount_lock);
+
+ if (unlikely(nd->flags & LOOKUP_BENEATH)) {
+ error = dirfd_path_init(nd);
+ if (unlikely(error))
+ return ERR_PTR(error);
+ nd->root = nd->path;
+ if (!(nd->flags & LOOKUP_RCU))
+ path_get(&nd->root);
+ }
if (*s == '/') {
if (likely(!nd->root.mnt))
set_root(nd);
@@ -2350,9 +2400,11 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
s = ERR_PTR(error);
return s;
}
- error = dirfd_path_init(nd);
- if (unlikely(error))
- return ERR_PTR(error);
+ if (likely(!nd->path.mnt)) {
+ error = dirfd_path_init(nd);
+ if (unlikely(error))
+ return ERR_PTR(error);
+ }
return s;
}
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 9138b4471dbf..7bc819ad0cd3 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -50,6 +50,13 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
#define LOOKUP_EMPTY 0x4000
#define LOOKUP_DOWN 0x8000
+/* Scoping flags for lookup. */
+#define LOOKUP_BENEATH 0x010000 /* No escaping from starting point. */
+#define LOOKUP_XDEV 0x020000 /* No mountpoint crossing. */
+#define LOOKUP_NO_MAGICLINKS 0x040000 /* No /proc/$pid/fd/ "symlink" crossing. */
+#define LOOKUP_NO_SYMLINKS 0x080000 /* No symlink crossing *at all*.
+ Implies LOOKUP_NO_MAGICLINKS. */
+
extern int path_pts(struct path *path);
extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty);
--
2.22.0
^ permalink raw reply related
* [PATCH v9 06/10] namei: LOOKUP_IN_ROOT: chroot-like path resolution
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Christian Brauner, Eric Biederman, Andy Lutomirski,
Andrew Morton, Alexei Starovoitov, Kees Cook, Jann Horn,
Tycho Andersen, David Drysdale, Chanho Min, Oleg Nesterov,
Aleksa Sarai, Linus Torvalds, containers, linux-alpha, linux-api,
linux-arch, linux-arm-kernel, linux-fsdevel, linux-ia64,
linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
The primary motivation for the need for this flag is container runtimes
which have to interact with malicious root filesystems in the host
namespaces. One of the first requirements for a container runtime to be
secure against a malicious rootfs is that they correctly scope symlinks
(that is, they should be scoped as though they are chroot(2)ed into the
container's rootfs) and ".."-style paths[*]. The already-existing
LOOKUP_XDEV and LOOKUP_NO_MAGICLINKS help defend against other potential
attacks in a malicious rootfs scenario.
Currently most container runtimes try to do this resolution in
userspace[1], causing many potential race conditions. In addition, the
"obvious" alternative (actually performing a {ch,pivot_}root(2))
requires a fork+exec (for some runtimes) which is *very* costly if
necessary for every filesystem operation involving a container.
[*] At the moment, ".." and magic-link jumping are disallowed for the
same reason it is disabled for LOOKUP_BENEATH -- currently it is not
safe to allow it. Future patches may enable it unconditionally once
we have resolved the possible races (for "..") and semantics (for
magic-link jumping).
The most significant *at(2) semantic change with LOOKUP_IN_ROOT is that
absolute pathnames no longer cause dirfd to be ignored completely. The
rationale is that LOOKUP_IN_ROOT must necessarily chroot-scope symlinks
with absolute paths to dirfd, and so doing it for the base path seems to
be the most consistent behaviour (and also avoids foot-gunning users who
want to scope paths that are absolute).
[1]: https://github.com/cyphar/filepath-securejoin
Co-developed-by: Christian Brauner <christian@brauner.io>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
fs/namei.c | 6 +++---
include/linux/namei.h | 1 +
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 9c3ed597466b..ff016b9e9082 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1149,7 +1149,7 @@ const char *get_link(struct nameidata *nd, bool trailing)
if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS))
return ERR_PTR(-ELOOP);
/* Not currently safe. */
- if (unlikely(nd->flags & LOOKUP_BENEATH))
+ if (unlikely(nd->flags & (LOOKUP_BENEATH | LOOKUP_IN_ROOT)))
return ERR_PTR(-EXDEV);
/*
* For trailing_symlink we check whether the symlink's
@@ -1833,7 +1833,7 @@ static inline int handle_dots(struct nameidata *nd, int type)
* cause our parent to have moved outside of the root and us to skip
* over it.
*/
- if (unlikely(nd->flags & LOOKUP_BENEATH))
+ if (unlikely(nd->flags & (LOOKUP_BENEATH | LOOKUP_IN_ROOT)))
return -EXDEV;
if (!nd->root.mnt)
set_root(nd);
@@ -2384,7 +2384,7 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->m_seq = read_seqbegin(&mount_lock);
- if (unlikely(nd->flags & LOOKUP_BENEATH)) {
+ if (unlikely(nd->flags & (LOOKUP_BENEATH | LOOKUP_IN_ROOT))) {
error = dirfd_path_init(nd);
if (unlikely(error))
return ERR_PTR(error);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 7bc819ad0cd3..4b1ee717cb14 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -56,6 +56,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
#define LOOKUP_NO_MAGICLINKS 0x040000 /* No /proc/$pid/fd/ "symlink" crossing. */
#define LOOKUP_NO_SYMLINKS 0x080000 /* No symlink crossing *at all*.
Implies LOOKUP_NO_MAGICLINKS. */
+#define LOOKUP_IN_ROOT 0x100000 /* Treat dirfd as %current->fs->root. */
extern int path_pts(struct path *path);
--
2.22.0
^ permalink raw reply related
* [PATCH v9 07/10] namei: aggressively check for nd->root escape on ".." resolution
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Jann Horn, Kees Cook, Eric Biederman,
Andy Lutomirski, Andrew Morton, Alexei Starovoitov,
Christian Brauner, Tycho Andersen, David Drysdale, Chanho Min,
Oleg Nesterov, Aleksa Sarai, Linus Torvalds, containers,
linux-alpha, linux-api, linux-arch, linux-arm-kernel,
linux-fsdevel, linux-ia64, linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
This patch allows for LOOKUP_BENEATH and LOOKUP_IN_ROOT to safely permit
".." resolution (in the case of LOOKUP_BENEATH the resolution will still
fail if ".." resolution would resolve a path outside of the root --
while LOOKUP_IN_ROOT will chroot(2)-style scope it). magic-link jumps
are still disallowed entirely because now they could result in
inconsistent behaviour if resolution encounters a subsequent "..".
The need for this patch is explained by observing there is a fairly
easy-to-exploit race condition with chroot(2) (and thus by extension
LOOKUP_IN_ROOT and LOOKUP_BENEATH if ".." is allowed) where a rename(2)
of a path can be used to "skip over" nd->root and thus escape to the
filesystem above nd->root.
thread1 [attacker]:
for (;;)
renameat2(AT_FDCWD, "/a/b/c", AT_FDCWD, "/a/d", RENAME_EXCHANGE);
thread2 [victim]:
for (;;)
resolveat(dirb, "b/c/../../etc/shadow", RESOLVE_IN_ROOT);
With fairly significant regularity, thread2 will resolve to
"/etc/shadow" rather than "/a/b/etc/shadow". There is also a similar
(though somewhat more privileged) attack using MS_MOVE.
With this patch, such cases will be detected *during* ".." resolution
(which is the weak point of chroot(2) -- since walking *into* a
subdirectory tautologically cannot result in you walking *outside*
nd->root -- except through a bind-mount or magic-link). By detecting
this at ".." resolution (rather than checking only at the end of the
entire resolution) we can both correct escapes by jumping back to the
root (in the case of LOOKUP_IN_ROOT), as well as avoid revealing to
attackers the structure of the filesystem outside of the root (through
timing attacks for instance).
In order to avoid a quadratic lookup with each ".." entry, we only
activate the slow path if a write through &rename_lock or &mount_lock
has occurred during path resolution (&rename_lock and &mount_lock are
re-taken to further optimise the lookup). Since the primary attack being
protected against is MS_MOVE or rename(2), not doing additional checks
unless a mount or rename have occurred avoids making the common case
slow.
The use of path_is_under() here might seem suspect, but on further
inspection of the most important race (a path was *inside* the root but
is now *outside*), there appears to be no attack potential:
* If path_is_under() occurs before the rename, then the path will be
resolved -- however the path was originally inside the root and thus
there is no escape (and to userspace it'd look like the rename
occurred after the path was resolved). If path_is_under() occurs
afterwards, the resolution is blocked.
* Subsequent ".." jumps are guaranteed to check path_is_under() -- by
construction, &rename_lock or &mount_lock must have been taken by
the attacker after path_is_under() returned in the victim. Thus ".."
will not be able to escape from the previously-inside-root path.
* Walking down in the moved path is still safe since the entire
subtree was moved (either by rename(2) or MS_MOVE) and because (as
discussed above) walking down is safe.
I have run a variant of the above attack in a loop on several machines
with this patch, and no instances of a breakout were detected. While
this is not concrete proof that this is safe, when combined with the
above argument it should lend some trustworthiness to this construction.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
fs/namei.c | 48 +++++++++++++++++++++++++++++++++---------------
1 file changed, 33 insertions(+), 15 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index ff016b9e9082..a3f527494791 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -491,7 +491,7 @@ struct nameidata {
struct path root;
struct inode *inode; /* path.dentry.d_inode */
unsigned int flags;
- unsigned seq, m_seq;
+ unsigned seq, m_seq, r_seq;
int last_type;
unsigned depth;
int total_link_count;
@@ -1828,19 +1828,35 @@ static inline int may_lookup(struct nameidata *nd)
static inline int handle_dots(struct nameidata *nd, int type)
{
if (type == LAST_DOTDOT) {
- /*
- * LOOKUP_BENEATH resolving ".." is not currently safe -- races can
- * cause our parent to have moved outside of the root and us to skip
- * over it.
- */
- if (unlikely(nd->flags & (LOOKUP_BENEATH | LOOKUP_IN_ROOT)))
- return -EXDEV;
+ int error = 0;
+
if (!nd->root.mnt)
set_root(nd);
- if (nd->flags & LOOKUP_RCU) {
- return follow_dotdot_rcu(nd);
- } else
- return follow_dotdot(nd);
+ if (nd->flags & LOOKUP_RCU)
+ error = follow_dotdot_rcu(nd);
+ else
+ error = follow_dotdot(nd);
+ if (error)
+ return error;
+
+ if (unlikely(nd->flags & (LOOKUP_BENEATH | LOOKUP_IN_ROOT))) {
+ bool m_retry = read_seqretry(&mount_lock, nd->m_seq);
+ bool r_retry = read_seqretry(&rename_lock, nd->r_seq);
+
+ /*
+ * Don't bother checking unless there's a racing
+ * rename(2) or MS_MOVE.
+ */
+ if (likely(!m_retry && !r_retry))
+ return 0;
+
+ if (m_retry && !(nd->flags & LOOKUP_RCU))
+ nd->m_seq = read_seqbegin(&mount_lock);
+ if (r_retry)
+ nd->r_seq = read_seqbegin(&rename_lock);
+ if (!path_is_under(&nd->path, &nd->root))
+ return -EXDEV;
+ }
}
return 0;
}
@@ -2361,6 +2377,11 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
nd->depth = 0;
+
+ nd->m_seq = read_seqbegin(&mount_lock);
+ if (unlikely(flags & (LOOKUP_BENEATH | LOOKUP_IN_ROOT)))
+ nd->r_seq = read_seqbegin(&rename_lock);
+
if (flags & LOOKUP_ROOT) {
struct dentry *root = nd->root.dentry;
struct inode *inode = root->d_inode;
@@ -2371,7 +2392,6 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
if (flags & LOOKUP_RCU) {
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
nd->root_seq = nd->seq;
- nd->m_seq = read_seqbegin(&mount_lock);
} else {
path_get(&nd->path);
}
@@ -2382,8 +2402,6 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->path.mnt = NULL;
nd->path.dentry = NULL;
- nd->m_seq = read_seqbegin(&mount_lock);
-
if (unlikely(nd->flags & (LOOKUP_BENEATH | LOOKUP_IN_ROOT))) {
error = dirfd_path_init(nd);
if (unlikely(error))
--
2.22.0
^ permalink raw reply related
* [PATCH v9 08/10] open: openat2(2) syscall
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Christian Brauner, Eric Biederman, Andy Lutomirski,
Andrew Morton, Alexei Starovoitov, Kees Cook, Jann Horn,
Tycho Andersen, David Drysdale, Chanho Min, Oleg Nesterov,
Aleksa Sarai, Linus Torvalds, containers, linux-alpha, linux-api,
linux-arch, linux-arm-kernel, linux-fsdevel, linux-ia64,
linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
The most obvious syscall to add support for the new LOOKUP_* scoping
flags would be openat(2). However, there are a few reasons to not do
this:
* The new LOOKUP_* flags are intended to be security features, and
openat(2) will silently ignore all unknown flags. This means that
users would need to avoid foot-gunning themselves constantly when
using this interface if it were part of openat(2).
* Resolution scoping feels like a different operation to the existing
O_* flags. And since openat(2) has limited flag space, it seems to be
quite wasteful to clutter it with 5 flags that are all
resolution-related. Arguably O_NOFOLLOW is also a resolution flag but
its entire purpose is to error out if you encounter a trailing
symlink -- not to scope resolution.
* Other systems would be able to reimplement this syscall allowing for
cross-OS standardisation rather than being hidden amongst O_* flags
which may result in it not being used by all the parties that might
want to use it (file servers, web servers, container runtimes, etc).
* It gives us the opportunity to iterate on the O_PATH interface. In
particular, the new @how->upgrade_mask field for fd re-opening is
only possible because we have a clean slate without needing to re-use
the ACC_MODE flag design nor the existing openat(2) @mode semantics.
To this end, we introduce the openat2(2) syscall. It provides all of the
features of openat(2) through the @how->flags argument, but also
also provides a new @how->resolve argument which exposes RESOLVE_* flags
that map to our new LOOKUP_* flags. It also eliminates the long-standing
ugliness of variadic-open(2) by embedding it in a struct.
In order to allow for userspace to lock down their usage of file
descriptor re-opening, openat2(2) has the ability for users to disallow
certain re-opening modes through @how->upgrade_mask. At the moment,
there is no UPGRADE_NOEXEC.
Co-developed-by: Christian Brauner <christian@brauner.io>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
arch/alpha/kernel/syscalls/syscall.tbl | 1 +
arch/arm/tools/syscall.tbl | 1 +
arch/arm64/include/asm/unistd.h | 2 +-
arch/arm64/include/asm/unistd32.h | 2 +
arch/ia64/kernel/syscalls/syscall.tbl | 1 +
arch/m68k/kernel/syscalls/syscall.tbl | 1 +
arch/microblaze/kernel/syscalls/syscall.tbl | 1 +
arch/mips/kernel/syscalls/syscall_n32.tbl | 1 +
arch/mips/kernel/syscalls/syscall_n64.tbl | 1 +
arch/mips/kernel/syscalls/syscall_o32.tbl | 1 +
arch/parisc/kernel/syscalls/syscall.tbl | 1 +
arch/powerpc/kernel/syscalls/syscall.tbl | 1 +
arch/s390/kernel/syscalls/syscall.tbl | 1 +
arch/sh/kernel/syscalls/syscall.tbl | 1 +
arch/sparc/kernel/syscalls/syscall.tbl | 1 +
arch/x86/entry/syscalls/syscall_32.tbl | 1 +
arch/x86/entry/syscalls/syscall_64.tbl | 1 +
arch/xtensa/kernel/syscalls/syscall.tbl | 1 +
fs/open.c | 136 ++++++++++++++------
include/linux/fcntl.h | 15 ++-
include/linux/fs.h | 4 +-
include/linux/syscalls.h | 14 +-
include/uapi/asm-generic/unistd.h | 5 +-
include/uapi/linux/fcntl.h | 38 ++++++
24 files changed, 186 insertions(+), 46 deletions(-)
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index 9e7704e44f6d..1703d048c141 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -461,6 +461,7 @@
530 common getegid sys_getegid
531 common geteuid sys_geteuid
532 common getppid sys_getppid
+533 common openat2 sys_openat2
# all other architectures have common numbers for new syscall, alpha
# is the exception.
534 common pidfd_send_signal sys_pidfd_send_signal
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index aaf479a9e92d..4ad262698396 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -447,3 +447,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+434 common openat2 sys_openat2
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index c9f8dd421c5f..0d4aa3e5389e 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -33,7 +33,7 @@
#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5)
#define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)
-#define __NR_compat_syscalls 434
+#define __NR_compat_syscalls 435
#endif
#define __ARCH_WANT_SYS_CLONE
diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index aa995920bd34..b134419c0421 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -875,6 +875,8 @@ __SYSCALL(__NR_fsconfig, sys_fsconfig)
__SYSCALL(__NR_fsmount, sys_fsmount)
#define __NR_fspick 433
__SYSCALL(__NR_fspick, sys_fspick)
+#define __NR_openat2 434
+__SYSCALL(__NR_openat2, sys_openat2)
/*
* Please add new compat syscalls above this comment and update
diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl
index e01df3f2f80d..28d954acf214 100644
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -354,3 +354,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+434 common openat2 sys_openat2
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index 7e3d0734b2f3..b744b1a1c80e 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -433,3 +433,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+434 common openat2 sys_openat2
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 26339e417695..bee07b73a898 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -439,3 +439,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+434 common openat2 sys_openat2
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index 0e2dd68ade57..a3ec5e27630a 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -372,3 +372,4 @@
431 n32 fsconfig sys_fsconfig
432 n32 fsmount sys_fsmount
433 n32 fspick sys_fspick
+434 n32 openat2 sys_openat2
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index 5eebfa0d155c..3503ac6ef482 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -348,3 +348,4 @@
431 n64 fsconfig sys_fsconfig
432 n64 fsmount sys_fsmount
433 n64 fspick sys_fspick
+434 n64 openat2 sys_openat2
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 3cc1374e02d0..e901367371c4 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -421,3 +421,4 @@
431 o32 fsconfig sys_fsconfig
432 o32 fsmount sys_fsmount
433 o32 fspick sys_fspick
+434 o32 openat2 sys_openat2 sys_openat2
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index c9e377d59232..5758b0826e4d 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -430,3 +430,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+434 common openat2 sys_openat2
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 103655d84b4b..9e8377d5b2f6 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -515,3 +515,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+434 common openat2 sys_openat2
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index e822b2964a83..d6e8eaa20d44 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -436,3 +436,4 @@
431 common fsconfig sys_fsconfig sys_fsconfig
432 common fsmount sys_fsmount sys_fsmount
433 common fspick sys_fspick sys_fspick
+434 common openat2 sys_openat2 sys_openat2
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index 016a727d4357..dc38733d264b 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -436,3 +436,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+434 common openat2 sys_openat2
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index e047480b1605..cfeb24ac5299 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -479,3 +479,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+434 common openat2 sys_openat2
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index ad968b7bac72..1d76a0e84f42 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -438,3 +438,4 @@
431 i386 fsconfig sys_fsconfig __ia32_sys_fsconfig
432 i386 fsmount sys_fsmount __ia32_sys_fsmount
433 i386 fspick sys_fspick __ia32_sys_fspick
+434 i386 openat2 sys_openat2 __ia32_sys_openat2
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index b4e6f9e6204a..828bade2e505 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -355,6 +355,7 @@
431 common fsconfig __x64_sys_fsconfig
432 common fsmount __x64_sys_fsmount
433 common fspick __x64_sys_fspick
+434 common openat2 __x64_sys_openat2
#
# x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index 5fa0ee1c8e00..78ed6e97d3ae 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -404,3 +404,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+434 common openat2 sys_openat2
diff --git a/fs/open.c b/fs/open.c
index bdca45528524..63278294d1d4 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -928,24 +928,32 @@ struct file *open_with_fake_path(const struct path *path, int flags,
}
EXPORT_SYMBOL(open_with_fake_path);
-static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
+static inline int build_open_flags(struct open_how how, struct open_flags *op)
{
int lookup_flags = 0;
- int acc_mode = ACC_MODE(flags);
+ int opath_mask = 0;
+ int acc_mode = ACC_MODE(how.flags);
+
+ if (how.resolve & ~VALID_RESOLVE_FLAGS)
+ return -EINVAL;
+ if (!(how.flags & (O_PATH | O_CREAT | __O_TMPFILE)) && how.mode != 0)
+ return -EINVAL;
+ if (memchr_inv(how.reserved, 0, sizeof(how.reserved)))
+ return -EINVAL;
/*
* Clear out all open flags we don't know about so that we don't report
* them in fcntl(F_GETFD) or similar interfaces.
*/
- flags &= VALID_OPEN_FLAGS;
+ how.flags &= VALID_OPEN_FLAGS;
- if (flags & (O_CREAT | __O_TMPFILE))
- op->mode = (mode & S_IALLUGO) | S_IFREG;
+ if (how.flags & (O_CREAT | __O_TMPFILE))
+ op->mode = (how.mode & S_IALLUGO) | S_IFREG;
else
op->mode = 0;
/* Must never be set by userspace */
- flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
+ how.flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
/*
* O_SYNC is implemented as __O_SYNC|O_DSYNC. As many places only
@@ -953,51 +961,70 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
* always set instead of having to deal with possibly weird behaviour
* for malicious applications setting only __O_SYNC.
*/
- if (flags & __O_SYNC)
- flags |= O_DSYNC;
+ if (how.flags & __O_SYNC)
+ how.flags |= O_DSYNC;
- if (flags & __O_TMPFILE) {
- if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
+ if (how.flags & __O_TMPFILE) {
+ if ((how.flags & O_TMPFILE_MASK) != O_TMPFILE)
return -EINVAL;
if (!(acc_mode & MAY_WRITE))
return -EINVAL;
- } else if (flags & O_PATH) {
+ } else if (how.flags & O_PATH) {
/*
* If we have O_PATH in the open flag. Then we
* cannot have anything other than the below set of flags
*/
- flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
+ how.flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
acc_mode = 0;
+
+ /* Allow userspace to restrict the re-opening of O_PATH fds. */
+ if (how.upgrade_mask & ~VALID_UPGRADE_FLAGS)
+ return -EINVAL;
+ if (!(how.upgrade_mask & UPGRADE_NOREAD))
+ opath_mask |= FMODE_PATH_READ;
+ if (!(how.upgrade_mask & UPGRADE_NOWRITE))
+ opath_mask |= FMODE_PATH_WRITE;
}
- op->open_flag = flags;
+ op->open_flag = how.flags;
/* O_TRUNC implies we need access checks for write permissions */
- if (flags & O_TRUNC)
+ if (how.flags & O_TRUNC)
acc_mode |= MAY_WRITE;
/* Allow the LSM permission hook to distinguish append
access from general write access. */
- if (flags & O_APPEND)
+ if (how.flags & O_APPEND)
acc_mode |= MAY_APPEND;
op->acc_mode = acc_mode;
- op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
- /* For O_PATH backwards-compatibility we default to an all-set mask. */
- op->opath_mask = FMODE_PATH_READ | FMODE_PATH_WRITE;
+ op->intent = how.flags & O_PATH ? 0 : LOOKUP_OPEN;
+ op->opath_mask = opath_mask;
- if (flags & O_CREAT) {
+ if (how.flags & O_CREAT) {
op->intent |= LOOKUP_CREATE;
- if (flags & O_EXCL)
+ if (how.flags & O_EXCL)
op->intent |= LOOKUP_EXCL;
}
- if (flags & O_DIRECTORY)
+ if (how.flags & O_DIRECTORY)
lookup_flags |= LOOKUP_DIRECTORY;
- if (!(flags & O_NOFOLLOW))
+ if (!(how.flags & O_NOFOLLOW))
lookup_flags |= LOOKUP_FOLLOW;
- if (flags & O_EMPTYPATH)
+ if (how.flags & O_EMPTYPATH)
lookup_flags |= LOOKUP_EMPTY;
+
+ if (how.resolve & RESOLVE_NO_XDEV)
+ lookup_flags |= LOOKUP_XDEV;
+ if (how.resolve & RESOLVE_NO_MAGICLINKS)
+ lookup_flags |= LOOKUP_NO_MAGICLINKS;
+ if (how.resolve & RESOLVE_NO_SYMLINKS)
+ lookup_flags |= LOOKUP_NO_SYMLINKS;
+ if (how.resolve & RESOLVE_BENEATH)
+ lookup_flags |= LOOKUP_BENEATH;
+ if (how.resolve & RESOLVE_IN_ROOT)
+ lookup_flags |= LOOKUP_IN_ROOT;
+
op->lookup_flags = lookup_flags;
return 0;
}
@@ -1016,8 +1043,14 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
struct file *file_open_name(struct filename *name, int flags, umode_t mode)
{
struct open_flags op;
- int err = build_open_flags(flags, mode, &op);
- return err ? ERR_PTR(err) : do_filp_open(AT_FDCWD, name, &op);
+ struct open_how how = {
+ .flags = flags,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+ int err = build_open_flags(how, &op);
+ if (err)
+ return ERR_PTR(err);
+ return do_filp_open(AT_FDCWD, name, &op);
}
/**
@@ -1048,17 +1081,22 @@ struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
const char *filename, int flags, umode_t mode)
{
struct open_flags op;
- int err = build_open_flags(flags, mode, &op);
+ struct open_how how = {
+ .flags = flags,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+ int err = build_open_flags(how, &op);
if (err)
return ERR_PTR(err);
return do_file_open_root(dentry, mnt, filename, &op);
}
EXPORT_SYMBOL(file_open_root);
-long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
+long do_sys_open(int dfd, const char __user *filename,
+ struct open_how *how)
{
struct open_flags op;
- int fd = build_open_flags(flags, mode, &op);
+ int fd = build_open_flags(*how, &op);
int empty = 0;
struct filename *tmp;
@@ -1071,7 +1109,7 @@ long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
if (!empty)
op.open_flag &= ~O_EMPTYPATH;
- fd = get_unused_fd_flags(flags);
+ fd = get_unused_fd_flags(how->flags);
if (fd >= 0) {
struct file *f = do_filp_open(dfd, tmp, &op);
if (IS_ERR(f)) {
@@ -1088,19 +1126,35 @@ long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
{
- if (force_o_largefile())
- flags |= O_LARGEFILE;
-
- return do_sys_open(AT_FDCWD, filename, flags, mode);
+ return ksys_open(filename, flags, mode);
}
SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
umode_t, mode)
{
+ struct open_how how = {
+ .flags = flags,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+
+ if (force_o_largefile())
+ how.flags |= O_LARGEFILE;
+
+ return do_sys_open(dfd, filename, &how);
+}
+
+SYSCALL_DEFINE3(openat2, int, dfd, const char __user *, filename,
+ const struct open_how __user *, how)
+{
+ struct open_how tmp;
+
+ if (copy_from_user(&tmp, how, sizeof(tmp)))
+ return -EFAULT;
+
if (force_o_largefile())
- flags |= O_LARGEFILE;
+ tmp.flags |= O_LARGEFILE;
- return do_sys_open(dfd, filename, flags, mode);
+ return do_sys_open(dfd, filename, &tmp);
}
#ifdef CONFIG_COMPAT
@@ -1110,7 +1164,11 @@ SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
*/
COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
{
- return do_sys_open(AT_FDCWD, filename, flags, mode);
+ struct open_how how = {
+ .flags = flags,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+ return do_sys_open(AT_FDCWD, filename, &how);
}
/*
@@ -1119,7 +1177,11 @@ COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t,
*/
COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
{
- return do_sys_open(dfd, filename, flags, mode);
+ struct open_how how = {
+ .flags = flags,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+ return do_sys_open(dfd, filename, &how);
}
#endif
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index 2868ae6c8fc1..e59917292213 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -4,13 +4,26 @@
#include <uapi/linux/fcntl.h>
-/* list of all valid flags for the open/openat flags argument: */
+/* Should open_how.mode be set for older syscalls wrappers? */
+#define OPENHOW_MODE(flags, mode) \
+ (((flags) | (O_CREAT | __O_TMPFILE)) ? (mode) : 0)
+
+/* List of all valid flags for the open/openat flags argument: */
#define VALID_OPEN_FLAGS \
(O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | \
O_APPEND | O_NDELAY | O_NONBLOCK | O_NDELAY | __O_SYNC | O_DSYNC | \
FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \
O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE | O_EMPTYPATH)
+/* List of all valid flags for the how->upgrade_mask argument: */
+#define VALID_UPGRADE_FLAGS \
+ (UPGRADE_NOWRITE | UPGRADE_NOREAD)
+
+/* List of all valid flags for the how->resolve argument: */
+#define VALID_RESOLVE_FLAGS \
+ (RESOLVE_NO_XDEV | RESOLVE_NO_MAGICLINKS | RESOLVE_NO_SYMLINKS | \
+ RESOLVE_BENEATH | RESOLVE_IN_ROOT)
+
#ifndef force_o_largefile
#define force_o_largefile() (!IS_ENABLED(CONFIG_ARCH_32BIT_OFF_T))
#endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f7df213405ea..a3aede2b3a91 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2515,8 +2515,8 @@ extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
struct file *filp);
extern int vfs_fallocate(struct file *file, int mode, loff_t offset,
loff_t len);
-extern long do_sys_open(int dfd, const char __user *filename, int flags,
- umode_t mode);
+extern long do_sys_open(int dfd, const char __user *filename,
+ struct open_how *how);
extern struct file *file_open_name(struct filename *, int, umode_t);
extern struct file *filp_open(const char *, int, umode_t);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 2bcef4c70183..227303532bb7 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1369,15 +1369,21 @@ static inline int ksys_close(unsigned int fd)
return __close_fd(current->files, fd);
}
-extern long do_sys_open(int dfd, const char __user *filename, int flags,
- umode_t mode);
+extern long do_sys_open(int dfd, const char __user *filename,
+ struct open_how *how);
static inline long ksys_open(const char __user *filename, int flags,
umode_t mode)
{
+ struct open_how how = {
+ .flags = flags,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+
if (force_o_largefile())
- flags |= O_LARGEFILE;
- return do_sys_open(AT_FDCWD, filename, flags, mode);
+ how.flags |= O_LARGEFILE;
+
+ return do_sys_open(AT_FDCWD, filename, &how);
}
extern long do_sys_truncate(const char __user *pathname, loff_t length);
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index a87904daf103..67486188918b 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -845,8 +845,11 @@ __SYSCALL(__NR_fsmount, sys_fsmount)
#define __NR_fspick 433
__SYSCALL(__NR_fspick, sys_fspick)
+#define __NR_openat2 435
+__SYSCALL(__NR_openat2, sys_openat2)
+
#undef __NR_syscalls
-#define __NR_syscalls 434
+#define __NR_syscalls 435
/*
* 32 bit systems traditionally used different
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index 1d338357df8a..b7c904f0fca9 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -93,5 +93,43 @@
#define AT_RECURSIVE 0x8000 /* Apply to the entire subtree */
+/**
+ * Arguments for how openat2(2) should open the target path. If @extra is zero,
+ * then openat2(2) is identical to openat(2).
+ *
+ * @flags: O_* flags (unknown flags ignored).
+ * @mode: O_CREAT file mode (ignored otherwise).
+ * @upgrade_mask: restrict how the O_PATH may be re-opened (ignored otherwise).
+ * @resolve: RESOLVE_* flags (-EINVAL on unknown flags).
+ * @reserved: reserved for future extensions, must be zeroed.
+ */
+struct open_how {
+ __u32 flags;
+ union {
+ __u16 mode;
+ __u16 upgrade_mask;
+ };
+ __u16 resolve;
+ __u64 reserved[7]; /* must be zeroed */
+};
+
+/* how->resolve flags for openat2(2). */
+#define RESOLVE_NO_XDEV 0x01 /* Block mount-point crossings
+ (includes bind-mounts). */
+#define RESOLVE_NO_MAGICLINKS 0x02 /* Block traversal through procfs-style
+ "magic-links". */
+#define RESOLVE_NO_SYMLINKS 0x04 /* Block traversal through all symlinks
+ (implies OEXT_NO_MAGICLINKS) */
+#define RESOLVE_BENEATH 0x08 /* Block "lexical" trickery like
+ "..", symlinks, and absolute
+ paths which escape the dirfd. */
+#define RESOLVE_IN_ROOT 0x10 /* Make all jumps to "/" and ".."
+ be scoped inside the dirfd
+ (similar to chroot(2)). */
+
+/* how->upgrade flags for openat2(2). */
+/* First bit is reserved for a future UPGRADE_NOEXEC flag. */
+#define UPGRADE_NOREAD 0x02 /* Block re-opening with MAY_READ. */
+#define UPGRADE_NOWRITE 0x04 /* Block re-opening with MAY_WRITE. */
#endif /* _UAPI_LINUX_FCNTL_H */
--
2.22.0
^ permalink raw reply related
* [PATCH v9 09/10] kselftest: save-and-restore errno to allow for %m formatting
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Eric Biederman, Andy Lutomirski, Andrew Morton,
Alexei Starovoitov, Kees Cook, Jann Horn, Christian Brauner,
Tycho Andersen, David Drysdale, Chanho Min, Oleg Nesterov,
Aleksa Sarai, Linus Torvalds, containers, linux-alpha, linux-api,
linux-arch, linux-arm-kernel, linux-fsdevel, linux-ia64,
linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
Previously, using "%m" in a ksft_* format string can result in strange
output because the errno value wasn't saved before calling other libc
functions. The solution is to simply save and restore the errno before
we format the user-supplied format string.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
tools/testing/selftests/kselftest.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h
index ec15c4f6af55..0ac49d91a260 100644
--- a/tools/testing/selftests/kselftest.h
+++ b/tools/testing/selftests/kselftest.h
@@ -10,6 +10,7 @@
#ifndef __KSELFTEST_H
#define __KSELFTEST_H
+#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdarg.h>
@@ -81,58 +82,68 @@ static inline void ksft_print_cnts(void)
static inline void ksft_print_msg(const char *msg, ...)
{
+ int saved_errno = errno;
va_list args;
va_start(args, msg);
printf("# ");
+ errno = saved_errno;
vprintf(msg, args);
va_end(args);
}
static inline void ksft_test_result_pass(const char *msg, ...)
{
+ int saved_errno = errno;
va_list args;
ksft_cnt.ksft_pass++;
va_start(args, msg);
printf("ok %d ", ksft_test_num());
+ errno = saved_errno;
vprintf(msg, args);
va_end(args);
}
static inline void ksft_test_result_fail(const char *msg, ...)
{
+ int saved_errno = errno;
va_list args;
ksft_cnt.ksft_fail++;
va_start(args, msg);
printf("not ok %d ", ksft_test_num());
+ errno = saved_errno;
vprintf(msg, args);
va_end(args);
}
static inline void ksft_test_result_skip(const char *msg, ...)
{
+ int saved_errno = errno;
va_list args;
ksft_cnt.ksft_xskip++;
va_start(args, msg);
printf("not ok %d # SKIP ", ksft_test_num());
+ errno = saved_errno;
vprintf(msg, args);
va_end(args);
}
static inline void ksft_test_result_error(const char *msg, ...)
{
+ int saved_errno = errno;
va_list args;
ksft_cnt.ksft_error++;
va_start(args, msg);
printf("not ok %d # error ", ksft_test_num());
+ errno = saved_errno;
vprintf(msg, args);
va_end(args);
}
@@ -152,10 +163,12 @@ static inline int ksft_exit_fail(void)
static inline int ksft_exit_fail_msg(const char *msg, ...)
{
+ int saved_errno = errno;
va_list args;
va_start(args, msg);
printf("Bail out! ");
+ errno = saved_errno;
vprintf(msg, args);
va_end(args);
@@ -178,10 +191,12 @@ static inline int ksft_exit_xpass(void)
static inline int ksft_exit_skip(const char *msg, ...)
{
if (msg) {
+ int saved_errno = errno;
va_list args;
va_start(args, msg);
printf("not ok %d # SKIP ", 1 + ksft_test_num());
+ errno = saved_errno;
vprintf(msg, args);
va_end(args);
} else {
--
2.22.0
^ permalink raw reply related
* [PATCH v9 10/10] selftests: add openat2(2) selftests
From: Aleksa Sarai @ 2019-07-06 14:57 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Eric Biederman, Andy Lutomirski, Andrew Morton,
Alexei Starovoitov, Kees Cook, Jann Horn, Christian Brauner,
Tycho Andersen, David Drysdale, Chanho Min, Oleg Nesterov,
Aleksa Sarai, Linus Torvalds, containers, linux-alpha, linux-api,
linux-arch, linux-arm-kernel, linux-fsdevel, linux-ia64,
linux-kernel
In-Reply-To: <20190706145737.5299-1-cyphar@cyphar.com>
Test all of the various openat2(2) flags, as well as how file
descriptor re-opening works. A small stress-test of a symlink-rename
attack is included to show that the protections against ".."-based
attacks are sufficient.
In addition, the memfd selftest is fixed to no longer depend on the
now-disallowed functionality of upgrading an O_RDONLY descriptor to
O_RDWR.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/memfd/memfd_test.c | 7 +-
tools/testing/selftests/openat2/.gitignore | 1 +
tools/testing/selftests/openat2/Makefile | 12 +
tools/testing/selftests/openat2/helpers.c | 162 +++++++
tools/testing/selftests/openat2/helpers.h | 114 +++++
.../testing/selftests/openat2/linkmode_test.c | 325 ++++++++++++++
.../selftests/openat2/rename_attack_test.c | 124 ++++++
.../testing/selftests/openat2/resolve_test.c | 395 ++++++++++++++++++
9 files changed, 1139 insertions(+), 2 deletions(-)
create mode 100644 tools/testing/selftests/openat2/.gitignore
create mode 100644 tools/testing/selftests/openat2/Makefile
create mode 100644 tools/testing/selftests/openat2/helpers.c
create mode 100644 tools/testing/selftests/openat2/helpers.h
create mode 100644 tools/testing/selftests/openat2/linkmode_test.c
create mode 100644 tools/testing/selftests/openat2/rename_attack_test.c
create mode 100644 tools/testing/selftests/openat2/resolve_test.c
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 9781ca79794a..42a27d029c10 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -37,6 +37,7 @@ TARGETS += powerpc
TARGETS += proc
TARGETS += pstore
TARGETS += ptrace
+TARGETS += openat2
TARGETS += rseq
TARGETS += rtc
TARGETS += seccomp
diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
index c67d32eeb668..e71df3d3e55d 100644
--- a/tools/testing/selftests/memfd/memfd_test.c
+++ b/tools/testing/selftests/memfd/memfd_test.c
@@ -925,7 +925,7 @@ static void test_share_mmap(char *banner, char *b_suffix)
*/
static void test_share_open(char *banner, char *b_suffix)
{
- int fd, fd2;
+ int procfd, fd, fd2;
printf("%s %s %s\n", memfd_str, banner, b_suffix);
@@ -950,13 +950,16 @@ static void test_share_open(char *banner, char *b_suffix)
mfd_assert_has_seals(fd, F_SEAL_WRITE | F_SEAL_SHRINK);
mfd_assert_has_seals(fd2, F_SEAL_WRITE | F_SEAL_SHRINK);
+ /* We cannot do a MAY_WRITE re-open of an O_RDONLY fd. */
+ procfd = mfd_assert_open(fd2, O_PATH, 0);
close(fd2);
- fd2 = mfd_assert_open(fd, O_RDWR, 0);
+ fd2 = mfd_assert_open(procfd, O_WRONLY, 0);
mfd_assert_add_seals(fd2, F_SEAL_SEAL);
mfd_assert_has_seals(fd, F_SEAL_WRITE | F_SEAL_SHRINK | F_SEAL_SEAL);
mfd_assert_has_seals(fd2, F_SEAL_WRITE | F_SEAL_SHRINK | F_SEAL_SEAL);
+ close(procfd);
close(fd2);
close(fd);
}
diff --git a/tools/testing/selftests/openat2/.gitignore b/tools/testing/selftests/openat2/.gitignore
new file mode 100644
index 000000000000..bd68f6c3fd07
--- /dev/null
+++ b/tools/testing/selftests/openat2/.gitignore
@@ -0,0 +1 @@
+/*_test
diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile
new file mode 100644
index 000000000000..8235a49928f6
--- /dev/null
+++ b/tools/testing/selftests/openat2/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+
+CFLAGS += -Wall -O2 -g
+TEST_GEN_PROGS := linkmode_test resolve_test rename_attack_test
+
+include ../lib.mk
+
+$(OUTPUT)/linkmode_test: linkmode_test.c helpers.o
+$(OUTPUT)/rename_attack_test: rename_attack_test.c helpers.o
+$(OUTPUT)/resolve_test: resolve_test.c helpers.o
+
+EXTRA_CLEAN = helpers.o $(wildcard /tmp/ksft-openat2-*)
diff --git a/tools/testing/selftests/openat2/helpers.c b/tools/testing/selftests/openat2/helpers.c
new file mode 100644
index 000000000000..c16213ff1946
--- /dev/null
+++ b/tools/testing/selftests/openat2/helpers.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Author: Aleksa Sarai <cyphar@cyphar.com>
+ * Copyright (C) 2018-2019 SUSE LLC.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <string.h>
+#include <syscall.h>
+#include <limits.h>
+
+#include "helpers.h"
+
+int sys_openat2(int dfd, const char *path, const struct open_how *how)
+{
+ int ret = syscall(__NR_openat2, dfd, path, how);
+ return ret >= 0 ? ret : -errno;
+}
+
+int sys_openat(int dfd, const char *path, const struct open_how *how)
+{
+ int ret = openat(dfd, path, how->flags, how->mode);
+ return ret >= 0 ? ret : -errno;
+}
+
+int sys_renameat2(int olddirfd, const char *oldpath,
+ int newdirfd, const char *newpath, unsigned int flags)
+{
+ int ret = syscall(__NR_renameat2, olddirfd, oldpath,
+ newdirfd, newpath, flags);
+ return ret >= 0 ? ret : -errno;
+}
+
+char *openat_flags(unsigned int flags)
+{
+ char *flagset, *accmode = "(none)";
+
+ switch (flags & 0x03) {
+ case O_RDWR:
+ accmode = "O_RDWR";
+ break;
+ case O_RDONLY:
+ accmode = "O_RDONLY";
+ break;
+ case O_WRONLY:
+ accmode = "O_WRONLY";
+ break;
+ }
+
+ E_asprintf(&flagset, "%s%s%s",
+ (flags & O_PATH) ? "O_PATH|" : "",
+ (flags & O_CREAT) ? "O_CREAT|" : "",
+ accmode);
+
+ return flagset;
+}
+
+char *openat2_flags(const struct open_how *how)
+{
+ char *p;
+ char *flags_set, *resolve_set, *acc_set, *set;
+
+ flags_set = openat_flags(how->flags);
+
+ E_asprintf(&resolve_set, "%s%s%s%s%s0",
+ (how->resolve & RESOLVE_NO_XDEV) ? "RESOLVE_NO_XDEV|" : "",
+ (how->resolve & RESOLVE_NO_MAGICLINKS) ? "RESOLVE_NO_MAGICLINKS|" : "",
+ (how->resolve & RESOLVE_NO_SYMLINKS) ? "RESOLVE_NO_SYMLINKS|" : "",
+ (how->resolve & RESOLVE_BENEATH) ? "RESOLVE_BENEATH|" : "",
+ (how->resolve & RESOLVE_IN_ROOT) ? "RESOLVE_IN_ROOT|" : "");
+
+ /* Remove trailing "|0". */
+ p = strstr(resolve_set, "|0");
+ if (p)
+ *p = '\0';
+
+ if (how->flags & O_PATH)
+ E_asprintf(&acc_set, ", upgrade_mask=%s%s0",
+ (how->upgrade_mask & UPGRADE_NOREAD) ? "UPGRADE_NOREAD|" : "",
+ (how->upgrade_mask & UPGRADE_NOWRITE) ? "UPGRADE_NOWRITE|" : "");
+ else if (how->flags & O_CREAT)
+ E_asprintf(&acc_set, ", mode=0%o", how->mode);
+ else
+ acc_set = strdup("");
+
+ /* Remove trailing "|0". */
+ p = strstr(acc_set, "|0");
+ if (p)
+ *p = '\0';
+
+ /* And now generate our flagset. */
+ E_asprintf(&set, "[flags=%s, resolve=%s%s]",
+ flags_set, resolve_set, acc_set);
+
+ free(flags_set);
+ free(resolve_set);
+ free(acc_set);
+ return set;
+}
+
+int touchat(int dfd, const char *path)
+{
+ int fd = openat(dfd, path, O_CREAT);
+ if (fd >= 0)
+ close(fd);
+ return fd;
+}
+
+char *fdreadlink(int fd)
+{
+ char *target, *tmp;
+
+ E_asprintf(&tmp, "/proc/self/fd/%d", fd);
+
+ target = malloc(PATH_MAX);
+ if (!target)
+ ksft_exit_fail_msg("fdreadlink: malloc failed\n");
+ memset(target, 0, PATH_MAX);
+
+ E_readlink(tmp, target, PATH_MAX);
+ free(tmp);
+ return target;
+}
+
+bool fdequal(int fd, int dfd, const char *path)
+{
+ char *fdpath, *dfdpath, *other;
+ bool cmp;
+
+ fdpath = fdreadlink(fd);
+ dfdpath = fdreadlink(dfd);
+
+ if (!path)
+ E_asprintf(&other, "%s", dfdpath);
+ else if (*path == '/')
+ E_asprintf(&other, "%s", path);
+ else
+ E_asprintf(&other, "%s/%s", dfdpath, path);
+
+ cmp = !strcmp(fdpath, other);
+ if (!cmp)
+ ksft_print_msg("fdequal: expected '%s' but got '%s'\n", other, fdpath);
+
+ free(fdpath);
+ free(dfdpath);
+ free(other);
+ return cmp;
+}
+
+void test_openat2_supported(void)
+{
+ struct open_how how = {};
+ int fd = sys_openat2(AT_FDCWD, ".", &how);
+ if (fd == -ENOSYS)
+ ksft_exit_skip("openat2(2) unsupported on this kernel\n");
+ if (fd < 0)
+ ksft_exit_fail_msg("openat2(2) supported check failed: %s\n", strerror(-fd));
+ close(fd);
+}
diff --git a/tools/testing/selftests/openat2/helpers.h b/tools/testing/selftests/openat2/helpers.h
new file mode 100644
index 000000000000..ccdd1fc874c2
--- /dev/null
+++ b/tools/testing/selftests/openat2/helpers.h
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Author: Aleksa Sarai <cyphar@cyphar.com>
+ * Copyright (C) 2018-2019 SUSE LLC.
+ */
+
+#ifndef __RESOLVEAT_H__
+#define __RESOLVEAT_H__
+
+#define _GNU_SOURCE
+#include <stdint.h>
+#include "../kselftest.h"
+
+#define ARRAY_LEN(X) (sizeof (X) / sizeof (*(X)))
+
+#ifndef SYS_openat2
+#ifndef __NR_openat2
+#define __NR_openat2 434
+#endif /* __NR_openat2 */
+#define SYS_openat2 __NR_openat2
+#endif /* SYS_openat2 */
+
+/**
+ * Arguments for how openat2(2) should open the target path. If @extra is zero,
+ * then openat2 is identical to openat(2). Only one of @mode or @upgrade_mask
+ * may be set at any given time.
+ *
+ * @flags: O_* flags (unknown flags ignored).
+ * @mode: O_CREAT file mode (ignored otherwise).
+ * @upgrade_mask: restrict how the O_PATH may be re-opened (ignored otherwise).
+ * @resolve: RESOLVE_* flags (-EINVAL on unknown flags).
+ * @reserved: reserved for future extensions, must be zeroed.
+ */
+struct open_how {
+ uint32_t flags;
+ union {
+ uint16_t mode;
+ uint16_t upgrade_mask;
+ };
+ uint16_t resolve;
+ uint64_t reserved[7]; /* must be zeroed */
+};
+
+#ifndef RESOLVE_INROOT
+/* how->resolve flags for openat2(2). */
+#define RESOLVE_NO_XDEV 0x01 /* Block mount-point crossings
+ (includes bind-mounts). */
+#define RESOLVE_NO_MAGICLINKS 0x02 /* Block traversal through procfs-style
+ "magic-links". */
+#define RESOLVE_NO_SYMLINKS 0x04 /* Block traversal through all symlinks
+ (implies OEXT_NO_MAGICLINKS) */
+#define RESOLVE_BENEATH 0x08 /* Block "lexical" trickery like
+ "..", symlinks, and absolute
+ paths which escape the dirfd. */
+#define RESOLVE_IN_ROOT 0x10 /* Make all jumps to "/" and ".."
+ be scoped inside the dirfd
+ (similar to chroot(2)). */
+#endif /* RESOLVE_IN_ROOT */
+
+#ifndef UPGRADE_NOREAD
+/* how->upgrade flags for openat2(2). */
+/* First bit is reserved for a future UPGRADE_NOEXEC flag. */
+#define UPGRADE_NOREAD 0x02 /* Block re-opening with MAY_READ. */
+#define UPGRADE_NOWRITE 0x04 /* Block re-opening with MAY_WRITE. */
+#endif /* UPGRADE_NOREAD */
+
+#ifndef O_EMPTYPATH
+#define O_EMPTYPATH 040000000
+#endif /* O_EMPTYPATH */
+
+#define E_func(func, ...) \
+ do { \
+ if (func(__VA_ARGS__) < 0) \
+ ksft_exit_fail_msg("%s:%d %s failed\n", \
+ __FILE__, __LINE__, #func);\
+ } while (0)
+
+#define E_mkdirat(...) E_func(mkdirat, __VA_ARGS__)
+#define E_symlinkat(...) E_func(symlinkat, __VA_ARGS__)
+#define E_touchat(...) E_func(touchat, __VA_ARGS__)
+#define E_readlink(...) E_func(readlink, __VA_ARGS__)
+#define E_fstatat(...) E_func(fstatat, __VA_ARGS__)
+#define E_asprintf(...) E_func(asprintf, __VA_ARGS__)
+#define E_fchdir(...) E_func(fchdir, __VA_ARGS__)
+#define E_mount(...) E_func(mount, __VA_ARGS__)
+#define E_unshare(...) E_func(unshare, __VA_ARGS__)
+#define E_setresuid(...) E_func(setresuid, __VA_ARGS__)
+#define E_chmod(...) E_func(chmod, __VA_ARGS__)
+
+#define E_assert(expr, msg, ...) \
+ do { \
+ if (!(expr)) \
+ ksft_exit_fail_msg("ASSERT(%s:%d) failed (%s): " msg "\n", \
+ __FILE__, __LINE__, #expr, ##__VA_ARGS__); \
+ } while (0)
+
+typedef int (*openfunc_t)(int dfd, const char *path, const struct open_how *how);
+
+int sys_openat2(int dfd, const char *path, const struct open_how *how);
+char *openat2_flags(const struct open_how *how);
+
+int sys_openat(int dfd, const char *path, const struct open_how *how);
+char *openat_flags(unsigned int flags);
+
+int sys_renameat2(int olddirfd, const char *oldpath,
+ int newdirfd, const char *newpath, unsigned int flags);
+
+int touchat(int dfd, const char *path);
+char *fdreadlink(int fd);
+bool fdequal(int fd, int dfd, const char *path);
+
+void test_openat2_supported(void);
+
+#endif /* __RESOLVEAT_H__ */
diff --git a/tools/testing/selftests/openat2/linkmode_test.c b/tools/testing/selftests/openat2/linkmode_test.c
new file mode 100644
index 000000000000..37124bf97fef
--- /dev/null
+++ b/tools/testing/selftests/openat2/linkmode_test.c
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Author: Aleksa Sarai <cyphar@cyphar.com>
+ * Copyright (C) 2018-2019 SUSE LLC.
+ */
+
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include "../kselftest.h"
+#include "helpers.h"
+
+static mode_t fdmode(int fd)
+{
+ char *fdpath;
+ struct stat statbuf;
+ mode_t mode;
+
+ E_asprintf(&fdpath, "/proc/self/fd/%d", fd);
+ E_fstatat(AT_FDCWD, fdpath, &statbuf, AT_SYMLINK_NOFOLLOW);
+ mode = (statbuf.st_mode & ~S_IFMT);
+ free(fdpath);
+
+ return mode;
+}
+
+static int reopen_proc(int fd, unsigned int flags)
+{
+ int ret, saved_errno;
+ char *fdpath;
+
+ E_asprintf(&fdpath, "/proc/self/fd/%d", fd);
+ ret = open(fdpath, flags);
+ saved_errno = errno;
+ free(fdpath);
+
+ return ret >= 0 ? ret : -saved_errno;
+}
+
+static int reopen_oemptypath(int fd, unsigned int flags)
+{
+ int ret = openat(fd, "", O_EMPTYPATH | flags);
+ return ret >= 0 ? ret : -errno;
+}
+
+struct reopen_test {
+ openfunc_t open;
+ mode_t chmod_mode;
+ struct {
+ struct open_how how;
+ mode_t mode;
+ int err;
+ } orig, new;
+};
+
+static bool reopen(int fd, struct reopen_test *test)
+{
+ int newfd;
+ mode_t proc_mode;
+ bool failed = false;
+
+ /* Check that the proc mode is correct. */
+ proc_mode = fdmode(fd);
+ if (proc_mode != test->orig.mode) {
+ ksft_print_msg("incorrect fdmode (got[%o] != want[%o])\n",
+ proc_mode, test->orig.mode);
+ failed = true;
+ }
+
+ /* Re-open through /proc. */
+ newfd = reopen_proc(fd, test->new.how.flags);
+ if (newfd != test->new.err && (newfd < 0 || test->new.err < 0)) {
+ ksft_print_msg("/proc failure (%d != %d [%s])\n",
+ newfd, test->new.err, strerror(-test->new.err));
+ failed = true;
+ }
+ if (newfd >= 0) {
+ proc_mode = fdmode(newfd);
+ if (proc_mode != test->new.mode) {
+ ksft_print_msg("/proc wrong fdmode (got[%o] != want[%o])\n",
+ proc_mode, test->new.mode);
+ failed = true;
+ }
+ close(newfd);
+ }
+
+ /* Re-open with O_EMPTYPATH. */
+ newfd = reopen_oemptypath(fd, test->new.how.flags);
+ if (newfd != test->new.err && (newfd < 0 || test->new.err < 0)) {
+ ksft_print_msg("O_EMPTYPATH failure (%d != %d [%s])\n",
+ newfd, test->new.err, strerror(-test->new.err));
+ failed = true;
+ }
+ if (newfd >= 0) {
+ proc_mode = fdmode(newfd);
+ if (proc_mode != test->new.mode) {
+ ksft_print_msg("O_EMPTYPATH wrong fdmode (got[%o] != want[%o])\n",
+ proc_mode, test->new.mode);
+ failed = true;
+ }
+ close(newfd);
+ }
+
+ return failed;
+}
+
+void test_reopen_ordinary(bool privileged)
+{
+ int fd;
+ int err_access = privileged ? 0 : -EACCES;
+ char tmpfile[] = "/tmp/ksft-openat2-reopen-testfile.XXXXXX";
+
+ fd = mkstemp(tmpfile);
+ E_assert(fd >= 0, "mkstemp failed: %m\n");
+ close(fd);
+
+ struct reopen_test tests[] = {
+ /* Re-opening with the same mode should succeed. */
+ { .open = sys_openat, .chmod_mode = 0400,
+ .orig.how.flags = O_RDONLY, .orig.mode = 0500,
+ .new.how.flags = O_RDONLY, .new.mode = 0500 },
+ { .open = sys_openat, .chmod_mode = 0200,
+ .orig.how.flags = O_WRONLY, .orig.mode = 0300,
+ .new.how.flags = O_WRONLY, .new.mode = 0300 },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.how.flags = O_RDWR, .orig.mode = 0700,
+ .new.how.flags = O_RDWR, .new.mode = 0700 },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.how.flags = O_RDWR, .orig.mode = 0700,
+ .new.how.flags = O_RDONLY, .new.mode = 0500 },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.how.flags = O_RDWR, .orig.mode = 0700,
+ .new.how.flags = O_WRONLY, .new.mode = 0300 },
+
+ /*
+ * Re-opening with a different mode will always fail (with an obvious
+ * carve-out for privileged users).
+ */
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.how.flags = O_RDONLY, .orig.mode = 0500,
+ .new.how.flags = O_WRONLY, .new.mode = 0300, .new.err = err_access },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.how.flags = O_WRONLY, .orig.mode = 0300,
+ .new.how.flags = O_RDONLY, .new.mode = 0500, .new.err = err_access },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.how.flags = O_RDONLY, .orig.mode = 0500,
+ .new.how.flags = O_RDWR, .new.mode = 0700, .new.err = err_access },
+ { .open = sys_openat, .chmod_mode = 0600,
+ .orig.how.flags = O_WRONLY, .orig.mode = 0300,
+ .new.how.flags = O_RDWR, .new.mode = 0700, .new.err = err_access },
+
+ /* Doubly so if they didn't even have permissions at open-time. */
+ { .open = sys_openat, .chmod_mode = 0400,
+ .orig.how.flags = O_RDONLY, .orig.mode = 0500,
+ .new.how.flags = O_WRONLY, .new.mode = 0300, .new.err = err_access },
+ { .open = sys_openat, .chmod_mode = 0200,
+ .orig.how.flags = O_WRONLY, .orig.mode = 0300,
+ .new.how.flags = O_RDONLY, .new.mode = 0500, .new.err = err_access },
+ { .open = sys_openat, .chmod_mode = 0400,
+ .orig.how.flags = O_RDONLY, .orig.mode = 0500,
+ .new.how.flags = O_RDWR, .new.mode = 0700, .new.err = err_access },
+ { .open = sys_openat, .chmod_mode = 0200,
+ .orig.how.flags = O_WRONLY, .orig.mode = 0300,
+ .new.how.flags = O_RDWR, .new.mode = 0700, .new.err = err_access },
+
+ /* O_PATH re-opens (of ordinary files) will always work. */
+ { .open = sys_openat, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0070,
+ .new.how.flags = O_WRONLY, .new.mode = 0300 },
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0070,
+ .new.how.flags = O_WRONLY, .new.mode = 0300 },
+
+ { .open = sys_openat, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0070,
+ .new.how.flags = O_RDONLY, .new.mode = 0500 },
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0070,
+ .new.how.flags = O_RDONLY, .new.mode = 0500 },
+
+ { .open = sys_openat, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0070,
+ .new.how.flags = O_RDWR, .new.mode = 0700 },
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0070,
+ .new.how.flags = O_RDWR, .new.mode = 0700 },
+
+ /*
+ * openat2(2) UPGRADE_NO* flags. In the privileged case, the re-open
+ * will work but the mode will still be scoped to the mode (or'd with
+ * the open acc_mode).
+ */
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0010,
+ .orig.how.upgrade_mask = UPGRADE_NOREAD | UPGRADE_NOWRITE,
+ .new.how.flags = O_RDONLY, .new.mode = 0500, .new.err = err_access },
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0010,
+ .orig.how.upgrade_mask = UPGRADE_NOREAD | UPGRADE_NOWRITE,
+ .new.how.flags = O_WRONLY, .new.mode = 0300, .new.err = err_access },
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0010,
+ .orig.how.upgrade_mask = UPGRADE_NOREAD | UPGRADE_NOWRITE,
+ .new.how.flags = O_RDWR, .new.mode = 0700, .new.err = err_access },
+
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0050,
+ .orig.how.upgrade_mask = UPGRADE_NOWRITE,
+ .new.how.flags = O_RDONLY, .new.mode = 0500 },
+
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0030,
+ .orig.how.upgrade_mask = UPGRADE_NOREAD,
+ .new.how.flags = O_WRONLY, .new.mode = 0300 },
+
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0030,
+ .orig.how.upgrade_mask = UPGRADE_NOREAD,
+ .new.how.flags = O_RDONLY, .new.mode = 0500, .new.err = err_access },
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0050,
+ .orig.how.upgrade_mask = UPGRADE_NOWRITE,
+ .new.how.flags = O_WRONLY, .new.mode = 0300, .new.err = err_access },
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0030,
+ .orig.how.upgrade_mask = UPGRADE_NOREAD,
+ .new.how.flags = O_RDWR, .new.mode = 0700, .new.err = err_access },
+ { .open = sys_openat2, .chmod_mode = 0000,
+ .orig.how.flags = O_PATH, .orig.mode = 0050,
+ .orig.how.upgrade_mask = UPGRADE_NOWRITE,
+ .new.how.flags = O_RDWR, .new.mode = 0700, .new.err = err_access },
+ };
+
+ for (int i = 0; i < ARRAY_LEN(tests); i++) {
+ int fd;
+ char *orig_flagset, *new_flagset;
+ struct reopen_test *test = &tests[i];
+ void (*resultfn)(const char *msg, ...) = ksft_test_result_pass;
+
+ E_chmod(tmpfile, test->chmod_mode);
+
+ fd = test->open(AT_FDCWD, tmpfile, &test->orig.how);
+ E_assert(fd >= 0, "open '%s' failed: %m\n", tmpfile);
+
+ /* Make sure that any EACCES we see is not from inode permissions. */
+ E_chmod(tmpfile, 0777);
+
+ if (reopen(fd, test))
+ resultfn = ksft_test_result_fail;
+
+ close(fd);
+
+ new_flagset = openat_flags(test->new.how.flags);
+ if (test->open == sys_openat)
+ orig_flagset = openat_flags(test->orig.how.flags);
+ else if (test->open == sys_openat2)
+ orig_flagset = openat2_flags(&test->orig.how);
+ else
+ ksft_exit_fail_msg("unknown test->open\n");
+
+ resultfn("%sordinary reopen of (orig[%s]=%s, new=%s) chmod=%.3o %s\n",
+ privileged ? "privileged " : "",
+ test->open == sys_openat ? "openat" : "openat2",
+ orig_flagset, new_flagset, test->chmod_mode,
+ test->new.err < 0 ? strerror(-test->new.err) : "works");
+
+ free(new_flagset);
+ free(orig_flagset);
+ }
+
+ unlink(tmpfile);
+}
+
+void test_openat2_cloexec_test(void)
+{
+ void (*resultfn)(const char *msg, ...) = ksft_test_result_pass;
+ struct open_how how = {
+ .flags = O_CLOEXEC | O_PATH | O_DIRECTORY,
+ };
+
+ int fd = sys_openat2(AT_FDCWD, ".", &how);
+ E_assert(fd >= 0, "open '.' failed: %m\n");
+
+ int flags = fcntl(fd, F_GETFD);
+ E_assert(flags >= 0, "F_GETFD failed: %m\n");
+
+ if (!(flags & FD_CLOEXEC))
+ resultfn = ksft_test_result_fail;
+
+ resultfn("openat2(O_CLOEXEC) works as expected\n");
+}
+
+int main(int argc, char **argv)
+{
+ bool privileged;
+
+ ksft_print_header();
+ test_openat2_supported();
+
+ /*
+ * Technically we should be checking CAP_DAC_OVERRIDE, but it's easier to
+ * just assume that euid=0 has the full capability set.
+ */
+ privileged = (geteuid() == 0);
+ if (!privileged)
+ ksft_test_result_skip("privileged tests require euid == 0\n");
+ else {
+ test_reopen_ordinary(privileged);
+
+ E_setresuid(65534, 65534, 65534);
+ privileged = (geteuid() == 0);
+ }
+
+ test_reopen_ordinary(privileged);
+ test_openat2_cloexec_test();
+
+ if (ksft_get_fail_cnt() + ksft_get_error_cnt() > 0)
+ ksft_exit_fail();
+ else
+ ksft_exit_pass();
+}
diff --git a/tools/testing/selftests/openat2/rename_attack_test.c b/tools/testing/selftests/openat2/rename_attack_test.c
new file mode 100644
index 000000000000..b5e2a68609f1
--- /dev/null
+++ b/tools/testing/selftests/openat2/rename_attack_test.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Author: Aleksa Sarai <cyphar@cyphar.com>
+ * Copyright (C) 2018-2019 SUSE LLC.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <syscall.h>
+#include <limits.h>
+#include <unistd.h>
+
+#include "../kselftest.h"
+#include "helpers.h"
+
+/* Construct a test directory with the following structure:
+ *
+ * root/
+ * |-- a/
+ * | `-- c/
+ * `-- b/
+ */
+int setup_testdir(void)
+{
+ int dfd;
+ char dirname[] = "/tmp/ksft-openat2-rename-attack.XXXXXX";
+
+ /* Make the top-level directory. */
+ if (!mkdtemp(dirname))
+ ksft_exit_fail_msg("setup_testdir: failed to create tmpdir\n");
+ dfd = open(dirname, O_PATH | O_DIRECTORY);
+ if (dfd < 0)
+ ksft_exit_fail_msg("setup_testdir: failed to open tmpdir\n");
+
+ E_mkdirat(dfd, "a", 0755);
+ E_mkdirat(dfd, "b", 0755);
+ E_mkdirat(dfd, "a/c", 0755);
+
+ return dfd;
+}
+
+/* Swap @dirfd/@a and @dirfd/@b constantly. Parent must kill this process. */
+pid_t spawn_attack(int dirfd, char *a, char *b)
+{
+ pid_t child = fork();
+ if (child != 0)
+ return child;
+
+ /* If the parent (the test process) dies, kill ourselves too. */
+ prctl(PR_SET_PDEATHSIG, SIGKILL);
+
+ /* Swap @a and @b. */
+ for (;;)
+ renameat2(dirfd, a, dirfd, b, RENAME_EXCHANGE);
+ exit(1);
+}
+
+#define ROUNDS 400000
+void test_rename_attack(void)
+{
+ int dfd, afd, escaped_count = 0;
+ void (*resultfn)(const char *msg, ...) = ksft_test_result_pass;
+ pid_t child;
+
+ dfd = setup_testdir();
+ afd = openat(dfd, "a", O_PATH);
+ if (afd < 0)
+ ksft_exit_fail_msg("test_rename_attack: failed to open 'a'\n");
+
+ child = spawn_attack(dfd, "a/c", "b");
+
+ for (int i = 0; i < ROUNDS; i++) {
+ int fd;
+ bool failed;
+ struct open_how how = {
+ .flags = O_PATH,
+ .resolve = RESOLVE_IN_ROOT,
+ };
+ char *victim_path = "c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../../c/../..";
+
+ fd = sys_openat2(afd, victim_path, &how);
+ if (fd < 0)
+ failed = (fd != -EXDEV);
+ else
+ failed = !fdequal(fd, afd, NULL);
+
+ escaped_count += failed;
+ close(fd);
+ }
+
+ if (escaped_count > 0)
+ resultfn = ksft_test_result_fail;
+
+ resultfn("rename attack fails (expected 0 breakouts in %d runs, got %d)\n",
+ ROUNDS, escaped_count);
+
+ /* Should be killed anyway, but might as well make sure. */
+ kill(child, SIGKILL);
+}
+
+int main(int argc, char **argv)
+{
+ ksft_print_header();
+ test_openat2_supported();
+
+ test_rename_attack();
+
+ if (ksft_get_fail_cnt() + ksft_get_error_cnt() > 0)
+ ksft_exit_fail();
+ else
+ ksft_exit_pass();
+}
diff --git a/tools/testing/selftests/openat2/resolve_test.c b/tools/testing/selftests/openat2/resolve_test.c
new file mode 100644
index 000000000000..7f109cf6126a
--- /dev/null
+++ b/tools/testing/selftests/openat2/resolve_test.c
@@ -0,0 +1,395 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Author: Aleksa Sarai <cyphar@cyphar.com>
+ * Copyright (C) 2018-2019 SUSE LLC.
+ */
+
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <sched.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include "../kselftest.h"
+#include "helpers.h"
+
+/*
+ * Construct a test directory with the following structure:
+ *
+ * root/
+ * |-- procexe -> /proc/self/exe
+ * |-- procroot -> /proc/self/root
+ * |-- root/
+ * |-- mnt/ [mountpoint]
+ * | |-- self -> ../mnt/
+ * | `-- absself -> /mnt/
+ * |-- etc/
+ * | `-- passwd
+ * |-- creatlink -> /newfile3
+ * |-- relsym -> etc/passwd
+ * |-- abssym -> /etc/passwd
+ * |-- abscheeky -> /cheeky
+ * |-- abscheeky -> /cheeky
+ * `-- cheeky/
+ * |-- absself -> /
+ * |-- self -> ../../root/
+ * |-- garbageself -> /../../root/
+ * |-- passwd -> ../cheeky/../cheeky/../etc/../etc/passwd
+ * |-- abspasswd -> /../cheeky/../cheeky/../etc/../etc/passwd
+ * |-- dotdotlink -> ../../../../../../../../../../../../../../etc/passwd
+ * `-- garbagelink -> /../../../../../../../../../../../../../../etc/passwd
+ */
+int setup_testdir(void)
+{
+ int dfd, tmpfd;
+ char dirname[] = "/tmp/ksft-openat2-testdir.XXXXXX";
+
+ /* Unshare and make /tmp a new directory. */
+ E_unshare(CLONE_NEWNS);
+ E_mount("", "/tmp", "", MS_PRIVATE, "");
+
+ /* Make the top-level directory. */
+ if (!mkdtemp(dirname))
+ ksft_exit_fail_msg("setup_testdir: failed to create tmpdir\n");
+ dfd = open(dirname, O_PATH | O_DIRECTORY);
+ if (dfd < 0)
+ ksft_exit_fail_msg("setup_testdir: failed to open tmpdir\n");
+
+ /* A sub-directory which is actually used for tests. */
+ E_mkdirat(dfd, "root", 0755);
+ tmpfd = openat(dfd, "root", O_PATH | O_DIRECTORY);
+ if (tmpfd < 0)
+ ksft_exit_fail_msg("setup_testdir: failed to open tmpdir\n");
+ close(dfd);
+ dfd = tmpfd;
+
+ E_symlinkat("/proc/self/exe", dfd, "procexe");
+ E_symlinkat("/proc/self/root", dfd, "procroot");
+ E_mkdirat(dfd, "root", 0755);
+
+ /* There is no mountat(2), so use chdir. */
+ E_mkdirat(dfd, "mnt", 0755);
+ E_fchdir(dfd);
+ E_mount("tmpfs", "./mnt", "tmpfs", MS_NOSUID | MS_NODEV, "");
+ E_symlinkat("../mnt/", dfd, "mnt/self");
+ E_symlinkat("/mnt/", dfd, "mnt/absself");
+
+ E_mkdirat(dfd, "etc", 0755);
+ E_touchat(dfd, "etc/passwd");
+
+ E_symlinkat("/newfile3", dfd, "creatlink");
+ E_symlinkat("etc/passwd", dfd, "relsym");
+ E_symlinkat("/etc/passwd", dfd, "abssym");
+ E_symlinkat("/cheeky", dfd, "abscheeky");
+
+ E_mkdirat(dfd, "cheeky", 0755);
+
+ E_symlinkat("/", dfd, "cheeky/absself");
+ E_symlinkat("../../root/", dfd, "cheeky/self");
+ E_symlinkat("/../../root/", dfd, "cheeky/garbageself");
+
+ E_symlinkat("../cheeky/../etc/../etc/passwd", dfd, "cheeky/passwd");
+ E_symlinkat("/../cheeky/../etc/../etc/passwd", dfd, "cheeky/abspasswd");
+
+ E_symlinkat("../../../../../../../../../../../../../../etc/passwd",
+ dfd, "cheeky/dotdotlink");
+ E_symlinkat("/../../../../../../../../../../../../../../etc/passwd",
+ dfd, "cheeky/garbagelink");
+
+ return dfd;
+}
+
+struct basic_test {
+ const char *dir;
+ const char *path;
+ struct open_how how;
+ bool pass;
+ union {
+ int err;
+ const char *path;
+ } out;
+};
+
+void test_openat2_opath_tests(void)
+{
+ int rootfd;
+ char *procselfexe;
+
+ E_asprintf(&procselfexe, "/proc/%d/exe", getpid());
+ rootfd = setup_testdir();
+
+ struct basic_test tests[] = {
+ /** RESOLVE_BENEATH **/
+ /* Attempts to cross dirfd should be blocked. */
+ { .path = "/", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/absself", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/absself", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "..", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "../root/", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/self", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/self", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/garbageself", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/garbageself", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ /* Only relative paths that stay inside dirfd should work. */
+ { .path = "root", .how.resolve = RESOLVE_BENEATH,
+ .out.path = "root", .pass = true },
+ { .path = "etc", .how.resolve = RESOLVE_BENEATH,
+ .out.path = "etc", .pass = true },
+ { .path = "etc/passwd", .how.resolve = RESOLVE_BENEATH,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "relsym", .how.resolve = RESOLVE_BENEATH,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/passwd", .how.resolve = RESOLVE_BENEATH,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/passwd", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abssym", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "/etc/passwd", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/abspasswd", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/abspasswd", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ /* Tricky paths should fail. */
+ { .path = "cheeky/dotdotlink", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/dotdotlink", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "cheeky/garbagelink", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "abscheeky/garbagelink", .how.resolve = RESOLVE_BENEATH,
+ .out.err = -EXDEV, .pass = false },
+
+ /** RESOLVE_IN_ROOT **/
+ /* All attempts to cross the dirfd will be scoped-to-root. */
+ { .path = "/", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = NULL, .pass = true },
+ { .path = "cheeky/absself", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = NULL, .pass = true },
+ { .path = "abscheeky/absself", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = NULL, .pass = true },
+ { .path = "..", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = NULL, .pass = true },
+ { .path = "../root/", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "../root/", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "cheeky/self", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "cheeky/garbageself", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "abscheeky/garbageself", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "root", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "root", .pass = true },
+ { .path = "etc", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc", .pass = true },
+ { .path = "etc/passwd", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "relsym", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/passwd", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/passwd", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abssym", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "/etc/passwd", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/abspasswd", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/abspasswd",.how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/dotdotlink", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/dotdotlink", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "/../../../../abscheeky/dotdotlink", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "cheeky/garbagelink", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "abscheeky/garbagelink", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ { .path = "/../../../../abscheeky/garbagelink", .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "etc/passwd", .pass = true },
+ /* O_CREAT should handle trailing symlinks correctly. */
+ { .path = "newfile1", .how.flags = O_CREAT,
+ .how.mode = 0700,
+ .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "newfile1", .pass = true },
+ { .path = "/newfile2", .how.flags = O_CREAT,
+ .how.mode = 0700,
+ .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "newfile2", .pass = true },
+ { .path = "/creatlink", .how.flags = O_CREAT,
+ .how.mode = 0700,
+ .how.resolve = RESOLVE_IN_ROOT,
+ .out.path = "newfile3", .pass = true },
+
+ /** RESOLVE_NO_XDEV **/
+ /* Crossing *down* into a mountpoint is disallowed. */
+ { .path = "mnt", .how.resolve = RESOLVE_NO_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "mnt/", .how.resolve = RESOLVE_NO_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "mnt/.", .how.resolve = RESOLVE_NO_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ /* Crossing *up* out of a mountpoint is disallowed. */
+ { .dir = "mnt", .path = ".", .how.resolve = RESOLVE_NO_XDEV,
+ .out.path = "mnt", .pass = true },
+ { .dir = "mnt", .path = "..", .how.resolve = RESOLVE_NO_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .dir = "mnt", .path = "../mnt", .how.resolve = RESOLVE_NO_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .dir = "mnt", .path = "self", .how.resolve = RESOLVE_NO_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .dir = "mnt", .path = "absself", .how.resolve = RESOLVE_NO_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ /* Jumping to "/" is ok, but later components cannot cross. */
+ { .dir = "mnt", .path = "/", .how.resolve = RESOLVE_NO_XDEV,
+ .out.path = "/", .pass = true },
+ { .dir = "/", .path = "/", .how.resolve = RESOLVE_NO_XDEV,
+ .out.path = "/", .pass = true },
+ { .path = "/proc/1", .how.resolve = RESOLVE_NO_XDEV,
+ .out.err = -EXDEV, .pass = false },
+ { .path = "/tmp", .how.resolve = RESOLVE_NO_XDEV,
+ .out.err = -EXDEV, .pass = false },
+
+ /** RESOLVE_NO_MAGICLINKS **/
+ /* Regular symlinks should work. */
+ { .path = "relsym", .how.resolve = RESOLVE_NO_MAGICLINKS,
+ .out.path = "etc/passwd", .pass = true },
+ /* Magic-links should not work. */
+ { .path = "procexe", .how.resolve = RESOLVE_NO_MAGICLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "/proc/self/exe", .how.resolve = RESOLVE_NO_MAGICLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "procroot/etc", .how.resolve = RESOLVE_NO_MAGICLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "/proc/self/root/etc", .how.resolve = RESOLVE_NO_MAGICLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "/proc/self/root/etc", .how.flags = O_NOFOLLOW,
+ .how.resolve = RESOLVE_NO_MAGICLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "/proc/self/exe", .how.flags = O_NOFOLLOW,
+ .how.resolve = RESOLVE_NO_MAGICLINKS,
+ .out.path = procselfexe, .pass = true },
+
+ /** RESOLVE_NO_SYMLINKS **/
+ /* Normal paths should work. */
+ { .path = ".", .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.path = NULL, .pass = true },
+ { .path = "root", .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.path = "root", .pass = true },
+ { .path = "etc", .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.path = "etc", .pass = true },
+ { .path = "etc/passwd", .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.path = "etc/passwd", .pass = true },
+ /* Regular symlinks are blocked. */
+ { .path = "relsym", .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "abssym", .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "cheeky/garbagelink", .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "abscheeky/garbagelink", .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "abscheeky/absself", .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ /* Trailing symlinks with NO_FOLLOW. */
+ { .path = "relsym", .how.flags = O_NOFOLLOW,
+ .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.path = "relsym", .pass = true },
+ { .path = "abssym", .how.flags = O_NOFOLLOW,
+ .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.path = "abssym", .pass = true },
+ { .path = "cheeky/garbagelink", .how.flags = O_NOFOLLOW,
+ .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.path = "cheeky/garbagelink", .pass = true },
+ { .path = "abscheeky/garbagelink", .how.flags = O_NOFOLLOW,
+ .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ { .path = "abscheeky/absself", .how.flags = O_NOFOLLOW,
+ .how.resolve = RESOLVE_NO_SYMLINKS,
+ .out.err = -ELOOP, .pass = false },
+ };
+
+ for (int i = 0; i < ARRAY_LEN(tests); i++) {
+ int dfd, fd;
+ bool failed;
+ void (*resultfn)(const char *msg, ...) = ksft_test_result_pass;
+ struct basic_test *test = &tests[i];
+ char *flagstr;
+
+ /* Auto-set O_PATH. */
+ if (!(test->how.flags & O_CREAT))
+ test->how.flags |= O_PATH;
+ flagstr = openat2_flags(&test->how);
+
+ if (test->dir)
+ dfd = openat(rootfd, test->dir, O_PATH | O_DIRECTORY);
+ else
+ dfd = dup(rootfd);
+ if (dfd < 0) {
+ resultfn = ksft_test_result_error;
+ goto next;
+ }
+
+ fd = sys_openat2(dfd, test->path, &test->how);
+ if (test->pass)
+ failed = (fd < 0 || !fdequal(fd, rootfd, test->out.path));
+ else
+ failed = (fd != test->out.err);
+ if (fd >= 0)
+ close(fd);
+ close(dfd);
+
+ if (failed)
+ resultfn = ksft_test_result_fail;
+
+next:
+ if (test->pass)
+ resultfn("openat2(root[%s], %s, %s) ==> %s\n",
+ test->dir ?: ".", test->path, flagstr,
+ test->out.path ?: ".");
+ else
+ resultfn("openat2(root[%s], %s, %s) ==> %d (%s)\n",
+ test->dir ?: ".", test->path, flagstr,
+ test->out.err, strerror(-test->out.err));
+ free(flagstr);
+ }
+
+ free(procselfexe);
+ close(rootfd);
+}
+
+int main(int argc, char **argv)
+{
+ ksft_print_header();
+ test_openat2_supported();
+
+ /* NOTE: We should be checking for CAP_SYS_ADMIN here... */
+ if (geteuid() != 0)
+ ksft_exit_skip("openat2(2) tests require euid == 0\n");
+
+ test_openat2_opath_tests();
+
+ if (ksft_get_fail_cnt() + ksft_get_error_cnt() > 0)
+ ksft_exit_fail();
+ else
+ ksft_exit_pass();
+}
--
2.22.0
^ permalink raw reply related
* Re: [PATCH v6 13/17] fs-verity: support builtin file signatures
From: Theodore Ts'o @ 2019-07-07 18:47 UTC (permalink / raw)
To: Eric Biggers
Cc: Darrick J . Wong, linux-api, Dave Chinner, linux-f2fs-devel,
linux-fscrypt, linux-fsdevel, Jaegeuk Kim, linux-integrity,
linux-ext4, Linus Torvalds, Christoph Hellwig, Victor Hsieh
In-Reply-To: <20190701153237.1777-14-ebiggers@kernel.org>
On Mon, Jul 01, 2019 at 08:32:33AM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> To meet some users' needs, add optional support for having fs-verity
> handle a portion of the authentication policy in the kernel. An
> ".fs-verity" keyring is created to which X.509 certificates can be
> added; then a sysctl 'fs.verity.require_signatures' can be set to cause
> the kernel to enforce that all fs-verity files contain a signature of
> their file measurement by a key in this keyring.
>
> See the "Built-in signature verification" section of
> Documentation/filesystems/fsverity.rst for the full documentation.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
Looks good, you can add:
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
^ permalink raw reply
* Re: [PATCH v6 14/17] ext4: add basic fs-verity support
From: Theodore Ts'o @ 2019-07-07 18:51 UTC (permalink / raw)
To: Eric Biggers
Cc: Darrick J . Wong, linux-api, Dave Chinner, linux-f2fs-devel,
linux-fscrypt, linux-fsdevel, Jaegeuk Kim, linux-integrity,
linux-ext4, Linus Torvalds, Christoph Hellwig, Victor Hsieh
In-Reply-To: <20190701153237.1777-15-ebiggers@kernel.org>
On Mon, Jul 01, 2019 at 08:32:34AM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> Add most of fs-verity support to ext4. fs-verity is a filesystem
> feature that enables transparent integrity protection and authentication
> of read-only files. It uses a dm-verity like mechanism at the file
> level: a Merkle tree is used to verify any block in the file in
> log(filesize) time. It is implemented mainly by helper functions in
> fs/verity/. See Documentation/filesystems/fsverity.rst for the full
> documentation.
>
> This commit adds all of ext4 fs-verity support except for the actual
> data verification, including:
>
> - Adding a filesystem feature flag and an inode flag for fs-verity.
>
> - Implementing the fsverity_operations to support enabling verity on an
> inode and reading/writing the verity metadata.
>
> - Updating ->write_begin(), ->write_end(), and ->writepages() to support
> writing verity metadata pages.
>
> - Calling the fs-verity hooks for ->open(), ->setattr(), and ->ioctl().
>
> ext4 stores the verity metadata (Merkle tree and fsverity_descriptor)
> past the end of the file, starting at the first 64K boundary beyond
> i_size. This approach works because (a) verity files are readonly, and
> (b) pages fully beyond i_size aren't visible to userspace but can be
> read/written internally by ext4 with only some relatively small changes
> to ext4. This approach avoids having to depend on the EA_INODE feature
> and on rearchitecturing ext4's xattr support to support paging
> multi-gigabyte xattrs into memory, and to support encrypting xattrs.
> Note that the verity metadata *must* be encrypted when the file is,
> since it contains hashes of the plaintext data.
>
> This patch incorporates work by Theodore Ts'o and Chandan Rajendra.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
Looks good. You can add:
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Thanks,
- Ted
^ permalink raw reply
* Re: [PATCH v6 15/17] ext4: add fs-verity read support
From: Theodore Ts'o @ 2019-07-07 18:54 UTC (permalink / raw)
To: Eric Biggers
Cc: Darrick J . Wong, linux-api, Dave Chinner, linux-f2fs-devel,
linux-fscrypt, linux-fsdevel, Jaegeuk Kim, linux-integrity,
linux-ext4, Linus Torvalds, Christoph Hellwig, Victor Hsieh
In-Reply-To: <20190701153237.1777-16-ebiggers@kernel.org>
On Mon, Jul 01, 2019 at 08:32:35AM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> Make ext4_mpage_readpages() verify data as it is read from fs-verity
> files, using the helper functions from fs/verity/.
>
> To support both encryption and verity simultaneously, this required
> refactoring the decryption workflow into a generic "post-read
> processing" workflow which can do decryption, verification, or both.
>
> The case where the ext4 block size is not equal to the PAGE_SIZE is not
> supported yet, since in that case ext4_mpage_readpages() sometimes falls
> back to block_read_full_page(), which does not support fs-verity yet.
>
> Co-developed-by: Theodore Ts'o <tytso@mit.edu>
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
Looks good. Since there's a S-o-B, some might claim that a
Reviewed-by: is not necessary, but to the extent that you modified
this code as well:
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
- Ted
^ permalink raw reply
* Re: [PATCH v6 16/17] ext4: update on-disk format documentation for fs-verity
From: Theodore Ts'o @ 2019-07-07 18:54 UTC (permalink / raw)
To: Eric Biggers
Cc: Darrick J . Wong, linux-api, Dave Chinner, linux-f2fs-devel,
linux-fscrypt, linux-fsdevel, Jaegeuk Kim, linux-integrity,
linux-ext4, Linus Torvalds, Christoph Hellwig, Victor Hsieh
In-Reply-To: <20190701153237.1777-17-ebiggers@kernel.org>
On Mon, Jul 01, 2019 at 08:32:36AM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> Document the format of verity files on ext4, and the corresponding inode
> and superblock flags.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
Looks good, you can add:
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Thanks!
- Ted
^ permalink raw reply
* Re: [PATCH v9 10/10] selftests: add openat2(2) selftests
From: Michael Ellerman @ 2019-07-08 1:15 UTC (permalink / raw)
To: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan
Cc: Aleksa Sarai, Eric Biederman, Andy Lutomirski, Andrew Morton,
Alexei Starovoitov, Kees Cook, Jann Horn, Christian Brauner,
Tycho Andersen, David Drysdale, Chanho Min, Oleg Nesterov,
Aleksa Sarai, Linus Torvalds, containers, linux-alpha, linux-api,
linux-arch, linux-arm-kernel, linux-fsdevel, linux-ia64,
linux-kernel
In-Reply-To: <20190706145737.5299-11-cyphar@cyphar.com>
Hi Aleksa,
A few minor comments below.
Aleksa Sarai <cyphar@cyphar.com> writes:
> diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile
> new file mode 100644
> index 000000000000..8235a49928f6
> --- /dev/null
> +++ b/tools/testing/selftests/openat2/Makefile
> @@ -0,0 +1,12 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +CFLAGS += -Wall -O2 -g
> +TEST_GEN_PROGS := linkmode_test resolve_test rename_attack_test
> +
> +include ../lib.mk
> +
> +$(OUTPUT)/linkmode_test: linkmode_test.c helpers.o
> +$(OUTPUT)/rename_attack_test: rename_attack_test.c helpers.o
> +$(OUTPUT)/resolve_test: resolve_test.c helpers.o
You don't need to tell make that foo depends on foo.c.
Also if you make the dependency be on helpers.c then you won't get an
intermediate helpers.o, and then you don't need to clean it.
So the above three lines could just be:
$(TEST_GEN_PROGS): helpers.c
> +EXTRA_CLEAN = helpers.o $(wildcard /tmp/ksft-openat2-*)
If you follow my advice above you don't need helpers.o in there.
Deleting things from /tmp is also a bit fishy on shared machines, ie. it
will error if those files happen to be owned by another user.
cheers
^ permalink raw reply
* Re: [PATCH v9 10/10] selftests: add openat2(2) selftests
From: Aleksa Sarai @ 2019-07-08 5:47 UTC (permalink / raw)
To: Michael Ellerman
Cc: Al Viro, Jeff Layton, J. Bruce Fields, Arnd Bergmann,
David Howells, Shuah Khan, Shuah Khan, Eric Biederman,
Andy Lutomirski, Andrew Morton, Alexei Starovoitov, Kees Cook,
Jann Horn, Christian Brauner, Tycho Andersen, David Drysdale,
Chanho Min, Oleg Nesterov, Aleksa Sarai, Linus Torvalds,
containers
In-Reply-To: <878st9iax4.fsf@concordia.ellerman.id.au>
[-- Attachment #1: Type: text/plain, Size: 1620 bytes --]
On 2019-07-08, Michael Ellerman <mpe@ellerman.id.au> wrote:
> Aleksa Sarai <cyphar@cyphar.com> writes:
> > diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile
> > new file mode 100644
> > index 000000000000..8235a49928f6
> > --- /dev/null
> > +++ b/tools/testing/selftests/openat2/Makefile
> > @@ -0,0 +1,12 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +CFLAGS += -Wall -O2 -g
> > +TEST_GEN_PROGS := linkmode_test resolve_test rename_attack_test
> > +
> > +include ../lib.mk
> > +
> > +$(OUTPUT)/linkmode_test: linkmode_test.c helpers.o
> > +$(OUTPUT)/rename_attack_test: rename_attack_test.c helpers.o
> > +$(OUTPUT)/resolve_test: resolve_test.c helpers.o
>
> You don't need to tell make that foo depends on foo.c.
>
> Also if you make the dependency be on helpers.c then you won't get an
> intermediate helpers.o, and then you don't need to clean it.
>
> So the above three lines could just be:
>
> $(TEST_GEN_PROGS): helpers.c
I had some trouble getting this to work (hence why I went with the
version in the patch), but it looks like this works. I'll include it in
the next set.
> > +EXTRA_CLEAN = helpers.o $(wildcard /tmp/ksft-openat2-*)
>
> If you follow my advice above you don't need helpers.o in there.
>
> Deleting things from /tmp is also a bit fishy on shared machines, ie. it
> will error if those files happen to be owned by another user.
Good point. I'll drop that hunk in the next set.
Thanks!
--
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>
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^ permalink raw reply
* Re: [PATCH ghak90 V6 02/10] audit: add container id
From: Richard Guy Briggs @ 2019-07-08 17:51 UTC (permalink / raw)
To: Paul Moore
Cc: Tycho Andersen, containers, linux-api, Linux-Audit Mailing List,
linux-fsdevel, LKML, netdev, netfilter-devel, sgrubb, omosnace,
dhowells, simo, Eric Paris, Serge Hallyn, ebiederm, nhorman
In-Reply-To: <CAHC9VhR4fudQanvZGYWMvCf7k2CU3q7e7n1Pi7hzC3v_zpVEdw@mail.gmail.com>
On 2019-05-29 11:29, Paul Moore wrote:
> On Wed, May 29, 2019 at 10:57 AM Tycho Andersen <tycho@tycho.ws> wrote:
> >
> > On Mon, Apr 08, 2019 at 11:39:09PM -0400, Richard Guy Briggs wrote:
> > > It is not permitted to unset the audit container identifier.
> > > A child inherits its parent's audit container identifier.
> >
> > ...
> >
> > > /**
> > > + * audit_set_contid - set current task's audit contid
> > > + * @contid: contid value
> > > + *
> > > + * Returns 0 on success, -EPERM on permission failure.
> > > + *
> > > + * Called (set) from fs/proc/base.c::proc_contid_write().
> > > + */
> > > +int audit_set_contid(struct task_struct *task, u64 contid)
> > > +{
> > > + u64 oldcontid;
> > > + int rc = 0;
> > > + struct audit_buffer *ab;
> > > + uid_t uid;
> > > + struct tty_struct *tty;
> > > + char comm[sizeof(current->comm)];
> > > +
> > > + task_lock(task);
> > > + /* Can't set if audit disabled */
> > > + if (!task->audit) {
> > > + task_unlock(task);
> > > + return -ENOPROTOOPT;
> > > + }
> > > + oldcontid = audit_get_contid(task);
> > > + read_lock(&tasklist_lock);
> > > + /* Don't allow the audit containerid to be unset */
> > > + if (!audit_contid_valid(contid))
> > > + rc = -EINVAL;
> > > + /* if we don't have caps, reject */
> > > + else if (!capable(CAP_AUDIT_CONTROL))
> > > + rc = -EPERM;
> > > + /* if task has children or is not single-threaded, deny */
> > > + else if (!list_empty(&task->children))
> > > + rc = -EBUSY;
> > > + else if (!(thread_group_leader(task) && thread_group_empty(task)))
> > > + rc = -EALREADY;
> > > + read_unlock(&tasklist_lock);
> > > + if (!rc)
> > > + task->audit->contid = contid;
> > > + task_unlock(task);
> > > +
> > > + if (!audit_enabled)
> > > + return rc;
> >
> > ...but it is allowed to change it (assuming
> > capable(CAP_AUDIT_CONTROL), of course)? Seems like this might be more
> > immediately useful since we still live in the world of majority
> > privileged containers if we didn't allow changing it, in addition to
> > un-setting it.
>
> The idea is that only container orchestrators should be able to
> set/modify the audit container ID, and since setting the audit
> container ID can have a significant effect on the records captured
> (and their routing to multiple daemons when we get there) modifying
> the audit container ID is akin to modifying the audit configuration
> which is why it is gated by CAP_AUDIT_CONTROL. The current thinking
> is that you would only change the audit container ID from one
> set/inherited value to another if you were nesting containers, in
> which case the nested container orchestrator would need to be granted
> CAP_AUDIT_CONTROL (which everyone to date seems to agree is a workable
> compromise). We did consider allowing for a chain of nested audit
> container IDs, but the implications of doing so are significant
> (implementation mess, runtime cost, etc.) so we are leaving that out
> of this effort.
We had previously discussed the idea of restricting
orchestrators/engines from only being able to set the audit container
identifier on their own descendants, but it was discarded. I've added a
check to ensure this is now enforced.
I've also added a check to ensure that a process can't set its own audit
container identifier and that if the identifier is already set, then the
orchestrator/engine must be in a descendant user namespace from the
orchestrator that set the previously inherited audit container
identifier.
> From a practical perspective, un-setting the audit container ID is
> pretty much the same as changing it from one set value to another so
> most of the above applies to that case as well.
>
> --
> paul moore
> www.paul-moore.com
- RGB
--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635
^ permalink raw reply
* Re: [PATCH for 5.2] rseq/selftests: Fix Thumb mode build failure on arm32
From: Mathieu Desnoyers @ 2019-07-08 17:58 UTC (permalink / raw)
To: shuah, Will Deacon, Linus Torvalds, stable
Cc: linux-kernel, Peter Zijlstra, Thomas Gleixner, Joel Fernandes,
Catalin Marinas, Dave Watson, Andi Kleen, linux-kselftest,
H. Peter Anvin, Chris Lameter, Russell King, Michael Kerrisk,
Paul E . McKenney, Paul Turner, Boqun Feng, Josh Triplett,
rostedt, Ben Maurer, linux-api, Andy Lutomirski
In-Reply-To: <20190630135613.19897-1-mathieu.desnoyers@efficios.com>
----- On Jun 30, 2019, at 9:56 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
> Using ".arm .inst" for the arm signature introduces build issues for
> programs compiled in Thumb mode because the assembler stays in the
> arm mode for the rest of the inline assembly. Revert to using a ".word"
> to express the signature as data instead.
>
> The choice of signature is a valid trap instruction on arm32 little
> endian, where both code and data are little endian.
>
> ARMv6+ big endian (BE8) generates mixed endianness code vs data:
> little-endian code and big-endian data. The data value of the signature
> needs to have its byte order reversed to generate the trap instruction.
>
> Prior to ARMv6, -mbig-endian generates big-endian code and data
> (which match), so the endianness of the data representation of the
> signature should not be reversed. However, the choice between BE32
> and BE8 is done by the linker, so we cannot know whether code and
> data endianness will be mixed before the linker is invoked. So rather
> than try to play tricks with the linker, the rseq signature is simply
> data (not a trap instruction) prior to ARMv6 on big endian. This is
> why the signature is expressed as data (.word) rather than as
> instruction (.inst) in assembler.
>
> Because a ".word" is used to emit the signature, it will be interpreted
> as a literal pool by a disassembler, not as an actual instruction.
> Considering that the signature is not meant to be executed except in
> scenarios where the program execution is completely bogus, this should
> not be an issue.
Now that 5.2 is out before this patch has been merged, can we please
integrate this patch through the kernel selftests or ARM tree so it
can be merged into the stable 5.2 branch ?
Thanks
Mathieu
>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Acked-by: Will Deacon <will.deacon@arm.com>
> CC: Peter Zijlstra <peterz@infradead.org>
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: Joel Fernandes <joelaf@google.com>
> CC: Catalin Marinas <catalin.marinas@arm.com>
> CC: Dave Watson <davejwatson@fb.com>
> CC: Will Deacon <will.deacon@arm.com>
> CC: Shuah Khan <shuah@kernel.org>
> CC: Andi Kleen <andi@firstfloor.org>
> CC: linux-kselftest@vger.kernel.org
> CC: "H . Peter Anvin" <hpa@zytor.com>
> CC: Chris Lameter <cl@linux.com>
> CC: Russell King <linux@arm.linux.org.uk>
> CC: Michael Kerrisk <mtk.manpages@gmail.com>
> CC: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
> CC: Paul Turner <pjt@google.com>
> CC: Boqun Feng <boqun.feng@gmail.com>
> CC: Josh Triplett <josh@joshtriplett.org>
> CC: Steven Rostedt <rostedt@goodmis.org>
> CC: Ben Maurer <bmaurer@fb.com>
> CC: linux-api@vger.kernel.org
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: Linus Torvalds <torvalds@linux-foundation.org>
> CC: Carlos O'Donell <carlos@redhat.com>
> CC: Florian Weimer <fweimer@redhat.com>
> ---
> tools/testing/selftests/rseq/rseq-arm.h | 61 ++++++++++++++++++---------------
> 1 file changed, 33 insertions(+), 28 deletions(-)
>
> diff --git a/tools/testing/selftests/rseq/rseq-arm.h
> b/tools/testing/selftests/rseq/rseq-arm.h
> index 84f28f147fb6..5943c816c07c 100644
> --- a/tools/testing/selftests/rseq/rseq-arm.h
> +++ b/tools/testing/selftests/rseq/rseq-arm.h
> @@ -6,6 +6,8 @@
> */
>
> /*
> + * - ARM little endian
> + *
> * RSEQ_SIG uses the udf A32 instruction with an uncommon immediate operand
> * value 0x5de3. This traps if user-space reaches this instruction by mistake,
> * and the uncommon operand ensures the kernel does not move the instruction
> @@ -22,36 +24,40 @@
> * def3 udf #243 ; 0xf3
> * e7f5 b.n <7f5>
> *
> - * pre-ARMv6 big endian code:
> - * e7f5 b.n <7f5>
> - * def3 udf #243 ; 0xf3
> + * - ARMv6+ big endian (BE8):
> *
> * ARMv6+ -mbig-endian generates mixed endianness code vs data: little-endian
> - * code and big-endian data. Ensure the RSEQ_SIG data signature matches code
> - * endianness. Prior to ARMv6, -mbig-endian generates big-endian code and data
> - * (which match), so there is no need to reverse the endianness of the data
> - * representation of the signature. However, the choice between BE32 and BE8
> - * is done by the linker, so we cannot know whether code and data endianness
> - * will be mixed before the linker is invoked.
> + * code and big-endian data. The data value of the signature needs to have its
> + * byte order reversed to generate the trap instruction:
> + *
> + * Data: 0xf3def5e7
> + *
> + * Translates to this A32 instruction pattern:
> + *
> + * e7f5def3 udf #24035 ; 0x5de3
> + *
> + * Translates to this T16 instruction pattern:
> + *
> + * def3 udf #243 ; 0xf3
> + * e7f5 b.n <7f5>
> + *
> + * - Prior to ARMv6 big endian (BE32):
> + *
> + * Prior to ARMv6, -mbig-endian generates big-endian code and data
> + * (which match), so the endianness of the data representation of the
> + * signature should not be reversed. However, the choice between BE32
> + * and BE8 is done by the linker, so we cannot know whether code and
> + * data endianness will be mixed before the linker is invoked. So rather
> + * than try to play tricks with the linker, the rseq signature is simply
> + * data (not a trap instruction) prior to ARMv6 on big endian. This is
> + * why the signature is expressed as data (.word) rather than as
> + * instruction (.inst) in assembler.
> */
>
> -#define RSEQ_SIG_CODE 0xe7f5def3
> -
> -#ifndef __ASSEMBLER__
> -
> -#define RSEQ_SIG_DATA \
> - ({ \
> - int sig; \
> - asm volatile ("b 2f\n\t" \
> - "1: .inst " __rseq_str(RSEQ_SIG_CODE) "\n\t" \
> - "2:\n\t" \
> - "ldr %[sig], 1b\n\t" \
> - : [sig] "=r" (sig)); \
> - sig; \
> - })
> -
> -#define RSEQ_SIG RSEQ_SIG_DATA
> -
> +#ifdef __ARMEB__
> +#define RSEQ_SIG 0xf3def5e7 /* udf #24035 ; 0x5de3 (ARMv6+) */
> +#else
> +#define RSEQ_SIG 0xe7f5def3 /* udf #24035 ; 0x5de3 */
> #endif
>
> #define rseq_smp_mb() __asm__ __volatile__ ("dmb" ::: "memory", "cc")
> @@ -125,8 +131,7 @@ do { \
> __rseq_str(table_label) ":\n\t" \
> ".word " __rseq_str(version) ", " __rseq_str(flags) "\n\t" \
> ".word " __rseq_str(start_ip) ", 0x0, " __rseq_str(post_commit_offset) ", 0x0, "
> __rseq_str(abort_ip) ", 0x0\n\t" \
> - ".arm\n\t" \
> - ".inst " __rseq_str(RSEQ_SIG_CODE) "\n\t" \
> + ".word " __rseq_str(RSEQ_SIG) "\n\t" \
> __rseq_str(label) ":\n\t" \
> teardown \
> "b %l[" __rseq_str(abort_label) "]\n\t"
> --
> 2.11.0
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
^ permalink raw reply
* Re: [PATCH ghak90 V6 02/10] audit: add container id
From: Richard Guy Briggs @ 2019-07-08 18:05 UTC (permalink / raw)
To: Paul Moore
Cc: Serge E. Hallyn, Tycho Andersen, containers, linux-api,
Linux-Audit Mailing List, linux-fsdevel, LKML, netdev,
netfilter-devel, sgrubb, omosnace, dhowells, simo, Eric Paris,
ebiederm, nhorman
In-Reply-To: <CAHC9VhThLiQzGYRUWmSuVfOC6QCDmA75BDB7Eg7V8HX4x7ymQg@mail.gmail.com>
On 2019-05-30 15:29, Paul Moore wrote:
> On Thu, May 30, 2019 at 1:09 PM Serge E. Hallyn <serge@hallyn.com> wrote:
> > On Wed, May 29, 2019 at 06:39:48PM -0400, Paul Moore wrote:
> > > On Wed, May 29, 2019 at 6:28 PM Tycho Andersen <tycho@tycho.ws> wrote:
> > > > On Wed, May 29, 2019 at 12:03:58PM -0400, Paul Moore wrote:
> > > > > On Wed, May 29, 2019 at 11:34 AM Tycho Andersen <tycho@tycho.ws> wrote:
> > > > > > On Wed, May 29, 2019 at 11:29:05AM -0400, Paul Moore wrote:
> > > > > > > On Wed, May 29, 2019 at 10:57 AM Tycho Andersen <tycho@tycho.ws> wrote:
> > > > > > > > On Mon, Apr 08, 2019 at 11:39:09PM -0400, Richard Guy Briggs wrote:
>
> ...
>
> > > > > > > The current thinking
> > > > > > > is that you would only change the audit container ID from one
> > > > > > > set/inherited value to another if you were nesting containers, in
> > > > > > > which case the nested container orchestrator would need to be granted
> > > > > > > CAP_AUDIT_CONTROL (which everyone to date seems to agree is a workable
> > > > > > > compromise).
> > > >
> > > > won't work in user namespaced containers, because they will never be
> > > > capable(CAP_AUDIT_CONTROL); so I don't think this will work for
> > > > nesting as is. But maybe nobody cares :)
> > >
> > > That's fun :)
> > >
> > > To be honest, I've never been a big fan of supporting nested
> > > containers from an audit perspective, so I'm not really too upset
> > > about this. The k8s/cri-o folks seem okay with this, or at least I
> > > haven't heard any objections; lxc folks, what do you have to say?
> >
> > I actually thought the answer to this (when last I looked, "some time" ago)
> > was that userspace should track an audit message saying "task X in
> > container Y is changing its auditid to Z", and then decide to also track Z.
> > This should be doable, but a lot of extra work in userspace.
> >
> > Per-userns containerids would also work. So task X1 is in containerid
> > 1 on the host and creates a new task Y in new userns; it continues to
> > be reported in init_user_ns as containerid 1 forever; but in its own
> > userns it can request to be known as some other containerid. Audit
> > socks would be per-userns, allowing root in a container to watch for
> > audit events in its own (and descendent) namespaces.
> >
> > But again I'm sure we've gone over all this in the last few years.
> >
> > I suppose we can look at this as a "first step", and talk about
> > making it user-ns-nestable later. But agreed it's not useful in a
> > lot of situations as is.
>
> [REMINDER: It is an "*audit* container ID" and not a general
> "container ID" ;) Smiley aside, I'm not kidding about that part.]
>
> I'm not interested in supporting/merging something that isn't useful;
> if this doesn't work for your use case then we need to figure out what
> would work. It sounds like nested containers are much more common in
> the lxc world, can you elaborate a bit more on this?
>
> As far as the possible solutions you mention above, I'm not sure I
> like the per-userns audit container IDs, I'd much rather just emit the
> necessary tracking information via the audit record stream and let the
> log analysis tools figure it out. However, the bigger question is how
> to limit (re)setting the audit container ID when you are in a non-init
> userns. For reasons already mentioned, using capable() is a non
> starter for everything but the initial userns, and using ns_capable()
> is equally poor as it essentially allows any userns the ability to
> munge it's audit container ID (obviously not good). It appears we
> need a different method for controlling access to the audit container
> ID.
We're not quite ready yet for multiple audit daemons and possibly not
yet for audit namespaces, but this is starting to look a lot like the
latter.
If we can't trust ns_capable() then why are we passing on
CAP_AUDIT_CONTROL? It is being passed down and not stripped purposely
by the orchestrator/engine. If ns_capable() isn't inherited how is it
gained otherwise? Can it be inserted by cotainer image? I think the
answer is "no". Either we trust ns_capable() or we have audit
namespaces (recommend based on user namespace) (or both).
At this point I would say we are at an impasse unless we trust
ns_capable() or we implement audit namespaces.
I don't think another mechanism to trust nested orchestrators/engines
will buy us anything.
Am I missing something?
> Punting this to a LSM hook is an obvious thing to do, and something we
> might want to do anyway, but currently audit doesn't rely on the LSM
> for proper/safe operation and I'm not sure I want to change that now.
>
> The next obvious thing is to create some sort of access control knob
> in audit itself. Perhaps an auditctl operation that would allow the
> administrator to specify which containers, via their corresponding
> audit container IDs, are allowed to change their audit container ID?
> The permission granting would need to be done in the init userns, but
> it would allow containers with a non-init userns the ability to change
> their audit container ID. We would probably still want a
> ns_capable(CAP_AUDIT_CONTROL) restriction in this case.
This auditctl knob of which you speak is an additional API, not changing
the existing proposed one.
> Does anyone else have any other ideas?
>
> --
> paul moore
> www.paul-moore.com
- RGB
--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635
^ permalink raw reply
* Re: [PATCH for 5.2] rseq/selftests: Fix Thumb mode build failure on arm32
From: shuah @ 2019-07-08 18:10 UTC (permalink / raw)
To: Mathieu Desnoyers, Will Deacon, Linus Torvalds, stable
Cc: linux-kernel, Peter Zijlstra, Thomas Gleixner, Joel Fernandes,
Catalin Marinas, Dave Watson, Andi Kleen, linux-kselftest,
H. Peter Anvin, Chris Lameter, Russell King, Michael Kerrisk,
Paul E . McKenney, Paul Turner, Boqun Feng, Josh Triplett,
rostedt, Ben Maurer, linux-api, Andy Lutomirski
In-Reply-To: <1154710388.12906.1562608719838.JavaMail.zimbra@efficios.com>
On 7/8/19 11:58 AM, Mathieu Desnoyers wrote:
> ----- On Jun 30, 2019, at 9:56 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
>
>> Using ".arm .inst" for the arm signature introduces build issues for
>> programs compiled in Thumb mode because the assembler stays in the
>> arm mode for the rest of the inline assembly. Revert to using a ".word"
>> to express the signature as data instead.
>>
>> The choice of signature is a valid trap instruction on arm32 little
>> endian, where both code and data are little endian.
>>
>> ARMv6+ big endian (BE8) generates mixed endianness code vs data:
>> little-endian code and big-endian data. The data value of the signature
>> needs to have its byte order reversed to generate the trap instruction.
>>
>> Prior to ARMv6, -mbig-endian generates big-endian code and data
>> (which match), so the endianness of the data representation of the
>> signature should not be reversed. However, the choice between BE32
>> and BE8 is done by the linker, so we cannot know whether code and
>> data endianness will be mixed before the linker is invoked. So rather
>> than try to play tricks with the linker, the rseq signature is simply
>> data (not a trap instruction) prior to ARMv6 on big endian. This is
>> why the signature is expressed as data (.word) rather than as
>> instruction (.inst) in assembler.
>>
>> Because a ".word" is used to emit the signature, it will be interpreted
>> as a literal pool by a disassembler, not as an actual instruction.
>> Considering that the signature is not meant to be executed except in
>> scenarios where the program execution is completely bogus, this should
>> not be an issue.
>
> Now that 5.2 is out before this patch has been merged, can we please
> integrate this patch through the kernel selftests or ARM tree so it
> can be merged into the stable 5.2 branch ?
>
I will apply it to selftests and send it for 5.3-rc1 and mark it for
stable.
thanks,
-- Shuah
^ permalink raw reply
* Re: [PATCH ghak90 V6 02/10] audit: add container id
From: Richard Guy Briggs @ 2019-07-08 18:12 UTC (permalink / raw)
To: Paul Moore
Cc: Tycho Andersen, Serge E. Hallyn, containers, linux-api,
Linux-Audit Mailing List, linux-fsdevel, LKML, netdev,
netfilter-devel, sgrubb, omosnace, dhowells, simo, Eric Paris,
ebiederm, nhorman
In-Reply-To: <CAHC9VhT5HPt9rCJoDutdvA3r1Y1GOHfpXe2eJ54atNC1=Vd8LA@mail.gmail.com>
On 2019-05-30 19:26, Paul Moore wrote:
> On Thu, May 30, 2019 at 5:29 PM Tycho Andersen <tycho@tycho.ws> wrote:
> > On Thu, May 30, 2019 at 03:29:32PM -0400, Paul Moore wrote:
> > >
> > > [REMINDER: It is an "*audit* container ID" and not a general
> > > "container ID" ;) Smiley aside, I'm not kidding about that part.]
> >
> > This sort of seems like a distinction without a difference; presumably
> > audit is going to want to differentiate between everything that people
> > in userspace call a container. So you'll have to support all this
> > insanity anyway, even if it's "not a container ID".
>
> That's not quite right. Audit doesn't care about what a container is,
> or is not, it also doesn't care if the "audit container ID" actually
> matches the ID used by the container engine in userspace and I think
> that is a very important line to draw. Audit is simply given a value
> which it calls the "audit container ID", it ensures that the value is
> inherited appropriately (e.g. children inherit their parent's audit
> container ID), and it uses the value in audit records to provide some
> additional context for log analysis. The distinction isn't limited to
> the value itself, but also to how it is used; it is an "audit
> container ID" and not a "container ID" because this value is
> exclusively for use by the audit subsystem. We are very intentionally
> not adding a generic container ID to the kernel. If the kernel does
> ever grow a general purpose container ID we will be one of the first
> ones in line to make use of it, but we are not going to be the ones to
> generically add containers to the kernel. Enough people already hate
> audit ;)
>
> > > I'm not interested in supporting/merging something that isn't useful;
> > > if this doesn't work for your use case then we need to figure out what
> > > would work. It sounds like nested containers are much more common in
> > > the lxc world, can you elaborate a bit more on this?
> > >
> > > As far as the possible solutions you mention above, I'm not sure I
> > > like the per-userns audit container IDs, I'd much rather just emit the
> > > necessary tracking information via the audit record stream and let the
> > > log analysis tools figure it out. However, the bigger question is how
> > > to limit (re)setting the audit container ID when you are in a non-init
> > > userns. For reasons already mentioned, using capable() is a non
> > > starter for everything but the initial userns, and using ns_capable()
> > > is equally poor as it essentially allows any userns the ability to
> > > munge it's audit container ID (obviously not good). It appears we
> > > need a different method for controlling access to the audit container
> > > ID.
> >
> > One option would be to make it a string, and have it be append only.
> > That should be safe with no checks.
> >
> > I know there was a long thread about what type to make this thing. I
> > think you could accomplish the append-only-ness with a u64 if you had
> > some rule about only allowing setting lower order bits than those that
> > are already set. With 4 bits for simplicity:
> >
> > 1100 # initial container id
> > 1100 -> 1011 # not allowed
> > 1100 -> 1101 # allowed, but now 1101 is set in stone since there are
> > # no lower order bits left
> >
> > There are probably fancier ways to do it if you actually understand
> > math :)
>
> ;)
>
> > Since userns nesting is limited to 32 levels (right now, IIRC), and
> > you have 64 bits, this might be reasonable. You could just teach
> > container engines to use the first say N bits for themselves, with a 1
> > bit for the barrier at the end.
>
> I like the creativity, but I worry that at some point these
> limitations are going to be raised (limits have a funny way of doing
> that over time) and we will be in trouble. I say "trouble" because I
> want to be able to quickly do an audit container ID comparison and
> we're going to pay a penalty for these larger values (we'll need this
> when we add multiple auditd support and the requisite record routing).
>
> Thinking about this makes me also realize we probably need to think a
> bit longer about audit container ID conflicts between orchestrators.
> Right now we just take the value that is given to us by the
> orchestrator, but if we want to allow multiple container orchestrators
> to work without some form of cooperation in userspace (I think we have
> to assume the orchestrators will not talk to each other) we likely
> need to have some way to block reuse of an audit container ID. We
> would either need to prevent the orchestrator from explicitly setting
> an audit container ID to a currently in use value, or instead generate
> the audit container ID in the kernel upon an event triggered by the
> orchestrator (e.g. a write to a /proc file). I suspect we should
> start looking at the idr code, I think we will need to make use of it.
To address this, I'd suggest that it is enforced to only allow the
setting of descendants and to maintain a master list of audit container
identifiers (with a hash table if necessary later) that includes the
container owner.
This also allows the orchestrator/engine to inject processes into
existing containers by checking that the audit container identifier is
only used again by the same owner.
I have working code for both.
> paul moore
> www.paul-moore.com
- RGB
--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635
^ permalink raw reply
* Re: [PATCH 2/9] security: Add hooks to rule on setting a watch [ver #5]
From: Stephen Smalley @ 2019-07-08 18:46 UTC (permalink / raw)
To: David Howells, viro
Cc: Casey Schaufler, Greg Kroah-Hartman, nicolas.dichtel, raven,
Christian Brauner, keyrings, linux-usb, linux-security-module,
linux-fsdevel, linux-api, linux-block, linux-kernel
In-Reply-To: <156173692760.15137.9636883182556029747.stgit@warthog.procyon.org.uk>
On 6/28/19 11:48 AM, David Howells wrote:
> Add security hooks that will allow an LSM to rule on whether or not a watch
> may be set. More than one hook is required as the watches watch different
> types of object.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Casey Schaufler <casey@schaufler-ca.com>
> cc: Stephen Smalley <sds@tycho.nsa.gov>
> cc: linux-security-module@vger.kernel.org
> ---
>
> include/linux/lsm_hooks.h | 22 ++++++++++++++++++++++
> include/linux/security.h | 15 +++++++++++++++
> security/security.c | 13 +++++++++++++
> 3 files changed, 50 insertions(+)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 47f58cfb6a19..f9d31f6445e4 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1413,6 +1413,20 @@
> * @ctx is a pointer in which to place the allocated security context.
> * @ctxlen points to the place to put the length of @ctx.
> *
> + * Security hooks for the general notification queue:
> + *
> + * @watch_key:
> + * Check to see if a process is allowed to watch for event notifications
> + * from a key or keyring.
> + * @watch: The watch object
> + * @key: The key to watch.
> + *
> + * @watch_devices:
> + * Check to see if a process is allowed to watch for event notifications
> + * from devices (as a global set).
> + * @watch: The watch object
It is difficult to evaluate these without at least one implementation of
each hook. I am unclear as to how any security module would use the
watch argument, since it has no security field/blob and does not appear
to contain any information that would be relevant to deciding whether or
not to permit the watch to be set.
> + *
> + *
> * Security hooks for using the eBPF maps and programs functionalities through
> * eBPF syscalls.
> *
> @@ -1688,6 +1702,10 @@ union security_list_options {
> int (*inode_notifysecctx)(struct inode *inode, void *ctx, u32 ctxlen);
> int (*inode_setsecctx)(struct dentry *dentry, void *ctx, u32 ctxlen);
> int (*inode_getsecctx)(struct inode *inode, void **ctx, u32 *ctxlen);
> +#ifdef CONFIG_WATCH_QUEUE
> + int (*watch_key)(struct watch *watch, struct key *key);
> + int (*watch_devices)(struct watch *watch);
> +#endif /* CONFIG_WATCH_QUEUE */
>
> #ifdef CONFIG_SECURITY_NETWORK
> int (*unix_stream_connect)(struct sock *sock, struct sock *other,
> @@ -1964,6 +1982,10 @@ struct security_hook_heads {
> struct hlist_head inode_notifysecctx;
> struct hlist_head inode_setsecctx;
> struct hlist_head inode_getsecctx;
> +#ifdef CONFIG_WATCH_QUEUE
> + struct hlist_head watch_key;
> + struct hlist_head watch_devices;
> +#endif /* CONFIG_WATCH_QUEUE */
> #ifdef CONFIG_SECURITY_NETWORK
> struct hlist_head unix_stream_connect;
> struct hlist_head unix_may_send;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 659071c2e57c..540863678355 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -57,6 +57,7 @@ struct mm_struct;
> struct fs_context;
> struct fs_parameter;
> enum fs_value_type;
> +struct watch;
>
> /* Default (no) options for the capable function */
> #define CAP_OPT_NONE 0x0
> @@ -392,6 +393,10 @@ void security_inode_invalidate_secctx(struct inode *inode);
> int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
> int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
> int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
> +#ifdef CONFIG_WATCH_QUEUE
> +int security_watch_key(struct watch *watch, struct key *key);
> +int security_watch_devices(struct watch *watch);
> +#endif /* CONFIG_WATCH_QUEUE */
> #else /* CONFIG_SECURITY */
>
> static inline int call_lsm_notifier(enum lsm_event event, void *data)
> @@ -1204,6 +1209,16 @@ static inline int security_inode_getsecctx(struct inode *inode, void **ctx, u32
> {
> return -EOPNOTSUPP;
> }
> +#ifdef CONFIG_WATCH_QUEUE
> +static inline int security_watch_key(struct watch *watch, struct key *key)
> +{
> + return 0;
> +}
> +static inline int security_watch_devices(struct watch *watch)
> +{
> + return 0;
> +}
> +#endif /* CONFIG_WATCH_QUEUE */
> #endif /* CONFIG_SECURITY */
>
> #ifdef CONFIG_SECURITY_NETWORK
> diff --git a/security/security.c b/security/security.c
> index 613a5c00e602..2c9919226ad1 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1917,6 +1917,19 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
> }
> EXPORT_SYMBOL(security_inode_getsecctx);
>
> +#ifdef CONFIG_WATCH_QUEUE
> +int security_watch_key(struct watch *watch, struct key *key)
> +{
> + return call_int_hook(watch_key, 0, watch, key);
> +}
> +
> +int security_watch_devices(struct watch *watch)
> +{
> + return call_int_hook(watch_devices, 0, watch);
> +}
> +
> +#endif /* CONFIG_WATCH_QUEUE */
> +
> #ifdef CONFIG_SECURITY_NETWORK
>
> int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk)
>
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