* [PATCH v11 1/9] fs: Add and use vfs_get_ioctl_handler()
2024-03-22 15:09 [PATCH v11 0/9] Landlock: IOCTL support Günther Noack
@ 2024-03-22 15:09 ` Günther Noack
2024-03-22 15:31 ` Arnd Bergmann
2024-03-22 15:09 ` [PATCH v11 2/9] landlock: Add IOCTL access right for character and block devices Günther Noack
` (7 subsequent siblings)
8 siblings, 1 reply; 12+ messages in thread
From: Günther Noack @ 2024-03-22 15:09 UTC (permalink / raw)
To: linux-security-module, Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Arnd Bergmann, Christian Brauner, Günther Noack
From: Mickaël Salaün <mic@digikod.net>
Add a new vfs_get_ioctl_handler() helper to identify if an IOCTL command
is handled by the first IOCTL layer. Each IOCTL command is now handled
by a dedicated function, and all of them use the same signature.
Apart from the VFS, this helper is also intended to be used by Landlock
to cleanly categorize VFS IOCTLs and create appropriate security
policies.
This is an alternative to a first RFC [1] and a proposal for a new LSM
hook [2].
By dereferencing some pointers only when required, this should also
slightly improve do_vfs_ioctl().
Remove (double) pointer castings on put_user() calls.
Remove potential double vfs_ioctl() call for FIONREAD.
Fix ioctl_file_clone_range() return type from long to int.
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20240219183539.2926165-1-mic@digikod.net [1]
Link: https://lore.kernel.org/r/20240309075320.160128-2-gnoack@google.com [2]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
---
fs/ioctl.c | 213 +++++++++++++++++++++++++++++++--------------
include/linux/fs.h | 6 ++
2 files changed, 155 insertions(+), 64 deletions(-)
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 76cf22ac97d7..d2b6691ded16 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -56,8 +56,9 @@ long vfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
}
EXPORT_SYMBOL(vfs_ioctl);
-static int ioctl_fibmap(struct file *filp, int __user *p)
+static int ioctl_fibmap(struct file *filp, unsigned int fd, unsigned long arg)
{
+ int __user *p = (void __user *)arg;
struct inode *inode = file_inode(filp);
struct super_block *sb = inode->i_sb;
int error, ur_block;
@@ -197,11 +198,12 @@ int fiemap_prep(struct inode *inode, struct fiemap_extent_info *fieinfo,
}
EXPORT_SYMBOL(fiemap_prep);
-static int ioctl_fiemap(struct file *filp, struct fiemap __user *ufiemap)
+static int ioctl_fiemap(struct file *filp, unsigned int fd, unsigned long arg)
{
struct fiemap fiemap;
struct fiemap_extent_info fieinfo = { 0, };
struct inode *inode = file_inode(filp);
+ struct fiemap __user *ufiemap = (void __user *)arg;
int error;
if (!inode->i_op->fiemap)
@@ -228,6 +230,18 @@ static int ioctl_fiemap(struct file *filp, struct fiemap __user *ufiemap)
return error;
}
+static int ioctl_figetbsz(struct file *file, unsigned int fd, unsigned long arg)
+{
+ struct inode *inode = file_inode(file);
+ int __user *argp = (void __user *)arg;
+
+ /* anon_bdev filesystems may not have a block size */
+ if (!inode->i_sb->s_blocksize)
+ return -EINVAL;
+
+ return put_user(inode->i_sb->s_blocksize, argp);
+}
+
static long ioctl_file_clone(struct file *dst_file, unsigned long srcfd,
u64 off, u64 olen, u64 destoff)
{
@@ -249,9 +263,15 @@ static long ioctl_file_clone(struct file *dst_file, unsigned long srcfd,
return ret;
}
-static long ioctl_file_clone_range(struct file *file,
- struct file_clone_range __user *argp)
+static int ioctl_ficlone(struct file *file, unsigned int fd, unsigned long arg)
+{
+ return ioctl_file_clone(file, arg, 0, 0, 0);
+}
+
+static int ioctl_file_clone_range(struct file *file, unsigned int fd,
+ unsigned long arg)
{
+ struct file_clone_range __user *argp = (void __user *)arg;
struct file_clone_range args;
if (copy_from_user(&args, argp, sizeof(args)))
@@ -292,6 +312,27 @@ static int ioctl_preallocate(struct file *filp, int mode, void __user *argp)
sr.l_len);
}
+static int ioctl_resvsp(struct file *filp, unsigned int fd, unsigned long arg)
+{
+ int __user *p = (void __user *)arg;
+
+ return ioctl_preallocate(filp, 0, p);
+}
+
+static int ioctl_unresvsp(struct file *filp, unsigned int fd, unsigned long arg)
+{
+ int __user *p = (void __user *)arg;
+
+ return ioctl_preallocate(filp, FALLOC_FL_PUNCH_HOLE, p);
+}
+
+static int ioctl_zero_range(struct file *filp, unsigned int fd, unsigned long arg)
+{
+ int __user *p = (void __user *)arg;
+
+ return ioctl_preallocate(filp, FALLOC_FL_ZERO_RANGE, p);
+}
+
/* on ia32 l_start is on a 32-bit boundary */
#if defined CONFIG_COMPAT && defined(CONFIG_X86_64)
/* just account for different alignment */
@@ -321,28 +362,41 @@ static int compat_ioctl_preallocate(struct file *file, int mode,
}
#endif
-static int file_ioctl(struct file *filp, unsigned int cmd, int __user *p)
+static ioctl_handler_t file_ioctl(unsigned int cmd)
{
switch (cmd) {
case FIBMAP:
- return ioctl_fibmap(filp, p);
+ return ioctl_fibmap;
case FS_IOC_RESVSP:
case FS_IOC_RESVSP64:
- return ioctl_preallocate(filp, 0, p);
+ return ioctl_resvsp;
case FS_IOC_UNRESVSP:
case FS_IOC_UNRESVSP64:
- return ioctl_preallocate(filp, FALLOC_FL_PUNCH_HOLE, p);
+ return ioctl_unresvsp;
case FS_IOC_ZERO_RANGE:
- return ioctl_preallocate(filp, FALLOC_FL_ZERO_RANGE, p);
+ return ioctl_zero_range;
}
- return -ENOIOCTLCMD;
+ return NULL;
+}
+
+static int ioctl_fioclex(struct file *file, unsigned int fd, unsigned long arg)
+{
+ set_close_on_exec(fd, 1);
+ return 0;
+}
+
+static int ioctl_fionclex(struct file *file, unsigned int fd, unsigned long arg)
+{
+ set_close_on_exec(fd, 0);
+ return 0;
}
-static int ioctl_fionbio(struct file *filp, int __user *argp)
+static int ioctl_fionbio(struct file *filp, unsigned int fd, unsigned long arg)
{
unsigned int flag;
int on, error;
+ int __user *argp = (void __user *)arg;
error = get_user(on, argp);
if (error)
@@ -362,11 +416,11 @@ static int ioctl_fionbio(struct file *filp, int __user *argp)
return error;
}
-static int ioctl_fioasync(unsigned int fd, struct file *filp,
- int __user *argp)
+static int ioctl_fioasync(struct file *filp, unsigned int fd, unsigned long arg)
{
unsigned int flag;
int on, error;
+ int __user *argp = (void __user *)arg;
error = get_user(on, argp);
if (error)
@@ -384,7 +438,22 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp,
return error < 0 ? error : 0;
}
-static int ioctl_fsfreeze(struct file *filp)
+static int ioctl_fioqsize(struct file *file, unsigned int fd, unsigned long arg)
+{
+ struct inode *inode = file_inode(file);
+ void __user *argp = (void __user *)arg;
+
+ if (S_ISDIR(inode->i_mode) || S_ISREG(inode->i_mode) ||
+ S_ISLNK(inode->i_mode)) {
+ loff_t res = inode_get_bytes(inode);
+
+ return copy_to_user(argp, &res, sizeof(res)) ? -EFAULT : 0;
+ }
+
+ return -ENOTTY;
+}
+
+static int ioctl_fsfreeze(struct file *filp, unsigned int fd, unsigned long arg)
{
struct super_block *sb = file_inode(filp)->i_sb;
@@ -401,7 +470,7 @@ static int ioctl_fsfreeze(struct file *filp)
return freeze_super(sb, FREEZE_HOLDER_USERSPACE);
}
-static int ioctl_fsthaw(struct file *filp)
+static int ioctl_fsthaw(struct file *filp, unsigned int fd, unsigned long arg)
{
struct super_block *sb = file_inode(filp)->i_sb;
@@ -414,9 +483,9 @@ static int ioctl_fsthaw(struct file *filp)
return thaw_super(sb, FREEZE_HOLDER_USERSPACE);
}
-static int ioctl_file_dedupe_range(struct file *file,
- struct file_dedupe_range __user *argp)
+static int ioctl_file_dedupe_range(struct file *file, unsigned int fd, unsigned long arg)
{
+ struct file_dedupe_range __user *argp = (void __user *)arg;
struct file_dedupe_range *same = NULL;
int ret;
unsigned long size;
@@ -454,6 +523,14 @@ static int ioctl_file_dedupe_range(struct file *file,
return ret;
}
+static int ioctl_fionread(struct file *filp, unsigned int fd, unsigned long arg)
+{
+ int __user *argp = (void __user *)arg;
+ struct inode *inode = file_inode(filp);
+
+ return put_user(i_size_read(inode) - filp->f_pos, argp);
+}
+
/**
* fileattr_fill_xflags - initialize fileattr with xflags
* @fa: fileattr pointer
@@ -702,8 +779,9 @@ int vfs_fileattr_set(struct mnt_idmap *idmap, struct dentry *dentry,
}
EXPORT_SYMBOL(vfs_fileattr_set);
-static int ioctl_getflags(struct file *file, unsigned int __user *argp)
+static int ioctl_getflags(struct file *file, unsigned int fd, unsigned long arg)
{
+ unsigned int __user *argp = (void __user *)arg;
struct fileattr fa = { .flags_valid = true }; /* hint only */
int err;
@@ -713,8 +791,9 @@ static int ioctl_getflags(struct file *file, unsigned int __user *argp)
return err;
}
-static int ioctl_setflags(struct file *file, unsigned int __user *argp)
+static int ioctl_setflags(struct file *file, unsigned int fd, unsigned long arg)
{
+ unsigned int __user *argp = (void __user *)arg;
struct mnt_idmap *idmap = file_mnt_idmap(file);
struct dentry *dentry = file->f_path.dentry;
struct fileattr fa;
@@ -733,8 +812,9 @@ static int ioctl_setflags(struct file *file, unsigned int __user *argp)
return err;
}
-static int ioctl_fsgetxattr(struct file *file, void __user *argp)
+static int ioctl_fsgetxattr(struct file *file, unsigned int fd, unsigned long arg)
{
+ struct fsxattr __user *argp = (void __user *)arg;
struct fileattr fa = { .fsx_valid = true }; /* hint only */
int err;
@@ -745,8 +825,9 @@ static int ioctl_fsgetxattr(struct file *file, void __user *argp)
return err;
}
-static int ioctl_fssetxattr(struct file *file, void __user *argp)
+static int ioctl_fssetxattr(struct file *file, unsigned int fd, unsigned long arg)
{
+ struct fsxattr __user *argp = (void __user *)arg;
struct mnt_idmap *idmap = file_mnt_idmap(file);
struct dentry *dentry = file->f_path.dentry;
struct fileattr fa;
@@ -764,94 +845,98 @@ static int ioctl_fssetxattr(struct file *file, void __user *argp)
}
/*
- * do_vfs_ioctl() is not for drivers and not intended to be EXPORT_SYMBOL()'d.
- * It's just a simple helper for sys_ioctl and compat_sys_ioctl.
+ * Return NULL when no handler exists for @cmd, or the appropriate function
+ * otherwise. This means that these handlers should never return -ENOIOCTLCMD.
*
* When you add any new common ioctls to the switches above and below,
* please ensure they have compatible arguments in compat mode.
*/
-static int do_vfs_ioctl(struct file *filp, unsigned int fd,
- unsigned int cmd, unsigned long arg)
+ioctl_handler_t vfs_get_ioctl_handler(struct file *filp, unsigned int cmd)
{
- void __user *argp = (void __user *)arg;
- struct inode *inode = file_inode(filp);
-
switch (cmd) {
case FIOCLEX:
- set_close_on_exec(fd, 1);
- return 0;
+ return ioctl_fioclex;
case FIONCLEX:
- set_close_on_exec(fd, 0);
- return 0;
+ return ioctl_fionclex;
case FIONBIO:
- return ioctl_fionbio(filp, argp);
+ return ioctl_fionbio;
case FIOASYNC:
- return ioctl_fioasync(fd, filp, argp);
+ return ioctl_fioasync;
case FIOQSIZE:
- if (S_ISDIR(inode->i_mode) || S_ISREG(inode->i_mode) ||
- S_ISLNK(inode->i_mode)) {
- loff_t res = inode_get_bytes(inode);
- return copy_to_user(argp, &res, sizeof(res)) ?
- -EFAULT : 0;
- }
-
- return -ENOTTY;
+ return ioctl_fioqsize;
case FIFREEZE:
- return ioctl_fsfreeze(filp);
+ return ioctl_fsfreeze;
case FITHAW:
- return ioctl_fsthaw(filp);
+ return ioctl_fsthaw;
case FS_IOC_FIEMAP:
- return ioctl_fiemap(filp, argp);
+ return ioctl_fiemap;
case FIGETBSZ:
- /* anon_bdev filesystems may not have a block size */
- if (!inode->i_sb->s_blocksize)
- return -EINVAL;
-
- return put_user(inode->i_sb->s_blocksize, (int __user *)argp);
+ return ioctl_figetbsz;
case FICLONE:
- return ioctl_file_clone(filp, arg, 0, 0, 0);
+ return ioctl_ficlone;
case FICLONERANGE:
- return ioctl_file_clone_range(filp, argp);
+ return ioctl_file_clone_range;
case FIDEDUPERANGE:
- return ioctl_file_dedupe_range(filp, argp);
+ return ioctl_file_dedupe_range;
case FIONREAD:
- if (!S_ISREG(inode->i_mode))
- return vfs_ioctl(filp, cmd, arg);
+ if (!S_ISREG(file_inode(filp)->i_mode))
+ break;
- return put_user(i_size_read(inode) - filp->f_pos,
- (int __user *)argp);
+ return ioctl_fionread;
case FS_IOC_GETFLAGS:
- return ioctl_getflags(filp, argp);
+ return ioctl_getflags;
case FS_IOC_SETFLAGS:
- return ioctl_setflags(filp, argp);
+ return ioctl_setflags;
case FS_IOC_FSGETXATTR:
- return ioctl_fsgetxattr(filp, argp);
+ return ioctl_fsgetxattr;
case FS_IOC_FSSETXATTR:
- return ioctl_fssetxattr(filp, argp);
+ return ioctl_fssetxattr;
default:
- if (S_ISREG(inode->i_mode))
- return file_ioctl(filp, cmd, argp);
+ if (S_ISREG(file_inode(filp)->i_mode))
+ return file_ioctl(cmd);
break;
}
- return -ENOIOCTLCMD;
+ /* Forwards call to vfs_ioctl(filp, cmd, arg) */
+ return NULL;
+}
+
+/*
+ * do_vfs_ioctl() is not for drivers and not intended to be EXPORT_SYMBOL()'d.
+ * It's just a simple helper for sys_ioctl and compat_sys_ioctl.
+ */
+static int do_vfs_ioctl(struct file *filp, unsigned int fd,
+ unsigned int cmd, unsigned long arg)
+{
+ ioctl_handler_t handler = vfs_get_ioctl_handler(filp, cmd);
+ int ret;
+
+ if (!handler)
+ return -ENOIOCTLCMD;
+
+ ret = (*handler)(filp, fd, arg);
+ /* Makes sure handle() really handles this command. */
+ if (WARN_ON_ONCE(ret == -ENOIOCTLCMD))
+ return -ENOTTY;
+
+ return ret;
}
SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1fbc72c5f112..92bf421aae83 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1904,6 +1904,12 @@ extern long compat_ptr_ioctl(struct file *file, unsigned int cmd,
#define compat_ptr_ioctl NULL
#endif
+typedef int (*ioctl_handler_t)(struct file *file, unsigned int fd,
+ unsigned long arg);
+
+extern ioctl_handler_t vfs_get_ioctl_handler(struct file *filp,
+ unsigned int cmd);
+
/*
* VFS file helper functions.
*/
--
2.44.0.396.g6e790dbe36-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread* Re: [PATCH v11 1/9] fs: Add and use vfs_get_ioctl_handler()
2024-03-22 15:09 ` [PATCH v11 1/9] fs: Add and use vfs_get_ioctl_handler() Günther Noack
@ 2024-03-22 15:31 ` Arnd Bergmann
2024-03-25 13:25 ` Günther Noack
0 siblings, 1 reply; 12+ messages in thread
From: Arnd Bergmann @ 2024-03-22 15:31 UTC (permalink / raw)
To: Günther Noack, linux-security-module,
Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Christian Brauner
On Fri, Mar 22, 2024, at 16:09, Günther Noack wrote:
> From: Mickaël Salaün <mic@digikod.net>
>
> Add a new vfs_get_ioctl_handler() helper to identify if an IOCTL command
> is handled by the first IOCTL layer. Each IOCTL command is now handled
> by a dedicated function, and all of them use the same signature.
Sorry I didn't already reply the previous time you sent this.
I don't really like the idea of going through another indirect
pointer for each of the ioctls here, both because of the
complexity at the source level, and the potential cost on
architectures that need heavy barriers around indirect
function calls.
> -static int ioctl_fibmap(struct file *filp, int __user *p)
> +static int ioctl_fibmap(struct file *filp, unsigned int fd, unsigned
> long arg)
> {
> + int __user *p = (void __user *)arg;
The new version doesn't seem like an improvement when you
need the extra type casts here.
As a completely different approach, would it perhaps be
sufficient to define security_file_ioctl_compat() in a
way that it may return a special error code signifying
"don't call into fops->{unlocked,compat}_ioctl"?
This way landlock could trivially allow ioctls on e.g.
normal file systems, sockets and block devices but prevent
them on character devices it does not trust.
Arnd
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH v11 1/9] fs: Add and use vfs_get_ioctl_handler()
2024-03-22 15:31 ` Arnd Bergmann
@ 2024-03-25 13:25 ` Günther Noack
0 siblings, 0 replies; 12+ messages in thread
From: Günther Noack @ 2024-03-25 13:25 UTC (permalink / raw)
To: Arnd Bergmann
Cc: linux-security-module, Mickaël Salaün, Jeff Xu,
Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov, Paul Moore,
Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Christian Brauner
On Fri, Mar 22, 2024 at 04:31:58PM +0100, Arnd Bergmann wrote:
> On Fri, Mar 22, 2024, at 16:09, Günther Noack wrote:
> > From: Mickaël Salaün <mic@digikod.net>
> >
> > Add a new vfs_get_ioctl_handler() helper to identify if an IOCTL command
> > is handled by the first IOCTL layer. Each IOCTL command is now handled
> > by a dedicated function, and all of them use the same signature.
>
> Sorry I didn't already reply the previous time you sent this.
> I don't really like the idea of going through another indirect
> pointer for each of the ioctls here, both because of the
> complexity at the source level, and the potential cost on
> architectures that need heavy barriers around indirect
> function calls.
>
> > -static int ioctl_fibmap(struct file *filp, int __user *p)
> > +static int ioctl_fibmap(struct file *filp, unsigned int fd, unsigned
> > long arg)
> > {
> > + int __user *p = (void __user *)arg;
>
> The new version doesn't seem like an improvement when you
> need the extra type casts here.
>
> As a completely different approach, would it perhaps be
> sufficient to define security_file_ioctl_compat() in a
> way that it may return a special error code signifying
> "don't call into fops->{unlocked,compat}_ioctl"?
>
> This way landlock could trivially allow ioctls on e.g.
> normal file systems, sockets and block devices but prevent
> them on character devices it does not trust.
Thank you for the review, Arnd! I gave your suggestion a shot and it seems
cleaner - I'll send an updated patch shortly.
—Günther
^ permalink raw reply [flat|nested] 12+ messages in thread
* [PATCH v11 2/9] landlock: Add IOCTL access right for character and block devices
2024-03-22 15:09 [PATCH v11 0/9] Landlock: IOCTL support Günther Noack
2024-03-22 15:09 ` [PATCH v11 1/9] fs: Add and use vfs_get_ioctl_handler() Günther Noack
@ 2024-03-22 15:09 ` Günther Noack
2024-03-22 15:09 ` [PATCH v11 3/9] selftests/landlock: Test IOCTL support Günther Noack
` (6 subsequent siblings)
8 siblings, 0 replies; 12+ messages in thread
From: Günther Noack @ 2024-03-22 15:09 UTC (permalink / raw)
To: linux-security-module, Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Günther Noack, Christian Brauner, Arnd Bergmann
Introduces the LANDLOCK_ACCESS_FS_IOCTL_DEV right
and increments the Landlock ABI version to 5.
This access right applies to device-custom IOCTL commands
when they are invoked on block or character device files.
Like the truncate right, this right is associated with a file
descriptor at the time of open(2), and gets respected even when the
file descriptor is used outside of the thread which it was originally
opened in.
Therefore, a newly enabled Landlock policy does not apply to file
descriptors which are already open.
If the LANDLOCK_ACCESS_FS_IOCTL_DEV right is handled, only a small
number of safe IOCTL commands will be permitted on newly opened device
files. These include FIOCLEX, FIONCLEX, FIONBIO and FIOASYNC, as well
as other IOCTL commands for regular files which are implemented in
fs/ioctl.c.
Noteworthy scenarios which require special attention:
TTY devices are often passed into a process from the parent process,
and so a newly enabled Landlock policy does not retroactively apply to
them automatically. In the past, TTY devices have often supported
IOCTL commands like TIOCSTI and some TIOCLINUX subcommands, which were
letting callers control the TTY input buffer (and simulate
keypresses). This should be restricted to CAP_SYS_ADMIN programs on
modern kernels though.
Known limitations:
The LANDLOCK_ACCESS_FS_IOCTL_DEV access right is a coarse-grained
control over IOCTL commands.
Landlock users may use path-based restrictions in combination with
their knowledge about the file system layout to control what IOCTLs
can be done.
Cc: Paul Moore <paul@paul-moore.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Günther Noack <gnoack@google.com>
---
include/uapi/linux/landlock.h | 35 ++++++++++---
security/landlock/fs.c | 52 ++++++++++++++++++--
security/landlock/limits.h | 2 +-
security/landlock/syscalls.c | 8 ++-
tools/testing/selftests/landlock/base_test.c | 2 +-
tools/testing/selftests/landlock/fs_test.c | 5 +-
6 files changed, 87 insertions(+), 17 deletions(-)
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 25c8d7677539..193733d833b1 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -128,7 +128,7 @@ struct landlock_net_port_attr {
* files and directories. Files or directories opened before the sandboxing
* are not subject to these restrictions.
*
- * A file can only receive these access rights:
+ * The following access rights apply only to files:
*
* - %LANDLOCK_ACCESS_FS_EXECUTE: Execute a file.
* - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access. Note that
@@ -138,12 +138,13 @@ struct landlock_net_port_attr {
* - %LANDLOCK_ACCESS_FS_READ_FILE: Open a file with read access.
* - %LANDLOCK_ACCESS_FS_TRUNCATE: Truncate a file with :manpage:`truncate(2)`,
* :manpage:`ftruncate(2)`, :manpage:`creat(2)`, or :manpage:`open(2)` with
- * ``O_TRUNC``. Whether an opened file can be truncated with
- * :manpage:`ftruncate(2)` is determined during :manpage:`open(2)`, in the
- * same way as read and write permissions are checked during
- * :manpage:`open(2)` using %LANDLOCK_ACCESS_FS_READ_FILE and
- * %LANDLOCK_ACCESS_FS_WRITE_FILE. This access right is available since the
- * third version of the Landlock ABI.
+ * ``O_TRUNC``. This access right is available since the third version of the
+ * Landlock ABI.
+ *
+ * Whether an opened file can be truncated with :manpage:`ftruncate(2)` or used
+ * with `ioctl(2)` is determined during :manpage:`open(2)`, in the same way as
+ * read and write permissions are checked during :manpage:`open(2)` using
+ * %LANDLOCK_ACCESS_FS_READ_FILE and %LANDLOCK_ACCESS_FS_WRITE_FILE.
*
* A directory can receive access rights related to files or directories. The
* following access right is applied to the directory itself, and the
@@ -198,13 +199,30 @@ struct landlock_net_port_attr {
* If multiple requirements are not met, the ``EACCES`` error code takes
* precedence over ``EXDEV``.
*
+ * The following access right applies both to files and directories:
+ *
+ * - %LANDLOCK_ACCESS_FS_IOCTL_DEV: Invoke :manpage:`ioctl(2)` commands on an opened
+ * character or block device.
+ *
+ * This access right applies to all `ioctl(2)` commands implemented by device
+ * drivers. However, the following common IOCTL commands continue to be
+ * invokable independent of the %LANDLOCK_ACCESS_FS_IOCTL_DEV right:
+ *
+ * ``FIOCLEX``, ``FIONCLEX``, ``FIONBIO``, ``FIOASYNC``, ``FIOQSIZE``,
+ * ``FIFREEZE``, ``FITHAW``, ``FS_IOC_FIEMAP``, ``FIGETBSZ``, ``FICLONE``,
+ * ``FICLONERANGE``, ``FIDEDUPERANGE``, ``FS_IOC_GETFLAGS``,
+ * ``FS_IOC_SETFLAGS``, ``FS_IOC_FSGETXATTR``, ``FS_IOC_FSSETXATTR``
+ *
+ * This access right is available since the fifth version of the Landlock
+ * ABI.
+ *
* .. warning::
*
* It is currently not possible to restrict some file-related actions
* accessible through these syscall families: :manpage:`chdir(2)`,
* :manpage:`stat(2)`, :manpage:`flock(2)`, :manpage:`chmod(2)`,
* :manpage:`chown(2)`, :manpage:`setxattr(2)`, :manpage:`utime(2)`,
- * :manpage:`ioctl(2)`, :manpage:`fcntl(2)`, :manpage:`access(2)`.
+ * :manpage:`fcntl(2)`, :manpage:`access(2)`.
* Future Landlock evolutions will enable to restrict them.
*/
/* clang-format off */
@@ -223,6 +241,7 @@ struct landlock_net_port_attr {
#define LANDLOCK_ACCESS_FS_MAKE_SYM (1ULL << 12)
#define LANDLOCK_ACCESS_FS_REFER (1ULL << 13)
#define LANDLOCK_ACCESS_FS_TRUNCATE (1ULL << 14)
+#define LANDLOCK_ACCESS_FS_IOCTL_DEV (1ULL << 15)
/* clang-format on */
/**
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index c15559432d3d..30b70d38ddcc 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -148,7 +148,8 @@ static struct landlock_object *get_inode_object(struct inode *const inode)
LANDLOCK_ACCESS_FS_EXECUTE | \
LANDLOCK_ACCESS_FS_WRITE_FILE | \
LANDLOCK_ACCESS_FS_READ_FILE | \
- LANDLOCK_ACCESS_FS_TRUNCATE)
+ LANDLOCK_ACCESS_FS_TRUNCATE | \
+ LANDLOCK_ACCESS_FS_IOCTL_DEV)
/* clang-format on */
/*
@@ -1335,8 +1336,10 @@ static int hook_file_alloc_security(struct file *const file)
static int hook_file_open(struct file *const file)
{
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
- access_mask_t open_access_request, full_access_request, allowed_access;
- const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE;
+ access_mask_t open_access_request, full_access_request, allowed_access,
+ optional_access;
+ const struct inode *inode = file_inode(file);
+ const bool is_device = S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode);
const struct landlock_ruleset *const dom =
get_fs_domain(landlock_cred(file->f_cred)->domain);
@@ -1354,6 +1357,10 @@ static int hook_file_open(struct file *const file)
* We look up more access than what we immediately need for open(), so
* that we can later authorize operations on opened files.
*/
+ optional_access = LANDLOCK_ACCESS_FS_TRUNCATE;
+ if (is_device)
+ optional_access |= LANDLOCK_ACCESS_FS_IOCTL_DEV;
+
full_access_request = open_access_request | optional_access;
if (is_access_to_paths_allowed(
@@ -1410,6 +1417,43 @@ static int hook_file_truncate(struct file *const file)
return -EACCES;
}
+static int hook_file_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ const struct inode *inode = file_inode(file);
+ const bool is_device = S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode);
+ access_mask_t required_access, allowed_access;
+
+ if (!is_device)
+ return 0;
+
+ /*
+ * We permit IOCTL commands which have a do_vfs_ioctl handler for the
+ * given file.
+ */
+ if (vfs_get_ioctl_handler(file, cmd))
+ return 0;
+
+ /*
+ * It is the access rights at the time of opening the file which
+ * determine whether IOCTL can be used on the opened file later.
+ *
+ * The access right is attached to the opened file in hook_file_open().
+ */
+ required_access = LANDLOCK_ACCESS_FS_IOCTL_DEV;
+ allowed_access = landlock_file(file)->allowed_access;
+ if ((allowed_access & required_access) == required_access)
+ return 0;
+
+ return -EACCES;
+}
+
+static int hook_file_ioctl_compat(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ return hook_file_ioctl(file, cmd, arg);
+}
+
static struct security_hook_list landlock_hooks[] __ro_after_init = {
LSM_HOOK_INIT(inode_free_security, hook_inode_free_security),
@@ -1432,6 +1476,8 @@ static struct security_hook_list landlock_hooks[] __ro_after_init = {
LSM_HOOK_INIT(file_alloc_security, hook_file_alloc_security),
LSM_HOOK_INIT(file_open, hook_file_open),
LSM_HOOK_INIT(file_truncate, hook_file_truncate),
+ LSM_HOOK_INIT(file_ioctl, hook_file_ioctl),
+ LSM_HOOK_INIT(file_ioctl_compat, hook_file_ioctl_compat),
};
__init void landlock_add_fs_hooks(void)
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index 93c9c6f91556..20fdb5ff3514 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -18,7 +18,7 @@
#define LANDLOCK_MAX_NUM_LAYERS 16
#define LANDLOCK_MAX_NUM_RULES U32_MAX
-#define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_TRUNCATE
+#define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_IOCTL_DEV
#define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
#define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS)
#define LANDLOCK_SHIFT_ACCESS_FS 0
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 6788e73b6681..9ae3dfa47443 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -149,7 +149,7 @@ static const struct file_operations ruleset_fops = {
.write = fop_dummy_write,
};
-#define LANDLOCK_ABI_VERSION 4
+#define LANDLOCK_ABI_VERSION 5
/**
* sys_landlock_create_ruleset - Create a new ruleset
@@ -321,7 +321,11 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
if (!path_beneath_attr.allowed_access)
return -ENOMSG;
- /* Checks that allowed_access matches the @ruleset constraints. */
+ /*
+ * Checks that allowed_access matches the @ruleset constraints and only
+ * consists of publicly visible access rights (as opposed to synthetic
+ * ones).
+ */
mask = landlock_get_raw_fs_access_mask(ruleset, 0);
if ((path_beneath_attr.allowed_access | mask) != mask)
return -EINVAL;
diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index 646f778dfb1e..d292b419ccba 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -75,7 +75,7 @@ TEST(abi_version)
const struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
};
- ASSERT_EQ(4, landlock_create_ruleset(NULL, 0,
+ ASSERT_EQ(5, landlock_create_ruleset(NULL, 0,
LANDLOCK_CREATE_RULESET_VERSION));
ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 2d6d9b43d958..0bcbbf594fd7 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -527,9 +527,10 @@ TEST_F_FORK(layout1, inval)
LANDLOCK_ACCESS_FS_EXECUTE | \
LANDLOCK_ACCESS_FS_WRITE_FILE | \
LANDLOCK_ACCESS_FS_READ_FILE | \
- LANDLOCK_ACCESS_FS_TRUNCATE)
+ LANDLOCK_ACCESS_FS_TRUNCATE | \
+ LANDLOCK_ACCESS_FS_IOCTL_DEV)
-#define ACCESS_LAST LANDLOCK_ACCESS_FS_TRUNCATE
+#define ACCESS_LAST LANDLOCK_ACCESS_FS_IOCTL_DEV
#define ACCESS_ALL ( \
ACCESS_FILE | \
--
2.44.0.396.g6e790dbe36-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v11 3/9] selftests/landlock: Test IOCTL support
2024-03-22 15:09 [PATCH v11 0/9] Landlock: IOCTL support Günther Noack
2024-03-22 15:09 ` [PATCH v11 1/9] fs: Add and use vfs_get_ioctl_handler() Günther Noack
2024-03-22 15:09 ` [PATCH v11 2/9] landlock: Add IOCTL access right for character and block devices Günther Noack
@ 2024-03-22 15:09 ` Günther Noack
2024-03-22 15:09 ` [PATCH v11 4/9] selftests/landlock: Test IOCTL with memfds Günther Noack
` (5 subsequent siblings)
8 siblings, 0 replies; 12+ messages in thread
From: Günther Noack @ 2024-03-22 15:09 UTC (permalink / raw)
To: linux-security-module, Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Günther Noack
Exercises Landlock's IOCTL feature in different combinations of
handling and permitting the LANDLOCK_ACCESS_FS_IOCTL_DEV right, and in
different combinations of using files and directories.
Signed-off-by: Günther Noack <gnoack@google.com>
---
tools/testing/selftests/landlock/fs_test.c | 236 ++++++++++++++++++++-
1 file changed, 233 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 0bcbbf594fd7..22229fe3e403 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -8,6 +8,7 @@
*/
#define _GNU_SOURCE
+#include <asm/termbits.h>
#include <fcntl.h>
#include <linux/landlock.h>
#include <linux/magic.h>
@@ -15,6 +16,7 @@
#include <stdio.h>
#include <string.h>
#include <sys/capability.h>
+#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/prctl.h>
#include <sys/sendfile.h>
@@ -23,6 +25,12 @@
#include <sys/vfs.h>
#include <unistd.h>
+/*
+ * Intentionally included last to work around header conflict.
+ * See https://sourceware.org/glibc/wiki/Synchronizing_Headers.
+ */
+#include <linux/fs.h>
+
#include "common.h"
#ifndef renameat2
@@ -735,6 +743,9 @@ static int create_ruleset(struct __test_metadata *const _metadata,
}
for (i = 0; rules[i].path; i++) {
+ if (!rules[i].access)
+ continue;
+
add_path_beneath(_metadata, ruleset_fd, rules[i].access,
rules[i].path);
}
@@ -3443,7 +3454,7 @@ TEST_F_FORK(layout1, truncate_unhandled)
LANDLOCK_ACCESS_FS_WRITE_FILE;
int ruleset_fd;
- /* Enable Landlock. */
+ /* Enables Landlock. */
ruleset_fd = create_ruleset(_metadata, handled, rules);
ASSERT_LE(0, ruleset_fd);
@@ -3526,7 +3537,7 @@ TEST_F_FORK(layout1, truncate)
LANDLOCK_ACCESS_FS_TRUNCATE;
int ruleset_fd;
- /* Enable Landlock. */
+ /* Enables Landlock. */
ruleset_fd = create_ruleset(_metadata, handled, rules);
ASSERT_LE(0, ruleset_fd);
@@ -3752,7 +3763,7 @@ TEST_F_FORK(ftruncate, open_and_ftruncate)
};
int fd, ruleset_fd;
- /* Enable Landlock. */
+ /* Enables Landlock. */
ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
ASSERT_LE(0, ruleset_fd);
enforce_ruleset(_metadata, ruleset_fd);
@@ -3829,6 +3840,16 @@ TEST_F_FORK(ftruncate, open_and_ftruncate_in_different_processes)
ASSERT_EQ(0, close(socket_fds[1]));
}
+/* Invokes the FS_IOC_GETFLAGS IOCTL and returns its errno or 0. */
+static int test_fs_ioc_getflags_ioctl(int fd)
+{
+ uint32_t flags;
+
+ if (ioctl(fd, FS_IOC_GETFLAGS, &flags) < 0)
+ return errno;
+ return 0;
+}
+
TEST(memfd_ftruncate)
{
int fd;
@@ -3845,6 +3866,215 @@ TEST(memfd_ftruncate)
ASSERT_EQ(0, close(fd));
}
+static int test_fionread_ioctl(int fd)
+{
+ size_t sz = 0;
+
+ if (ioctl(fd, FIONREAD, &sz) < 0 && errno == EACCES)
+ return errno;
+ return 0;
+}
+
+/* clang-format off */
+FIXTURE(ioctl) {};
+
+FIXTURE_SETUP(ioctl) {};
+
+FIXTURE_TEARDOWN(ioctl) {};
+/* clang-format on */
+
+FIXTURE_VARIANT(ioctl)
+{
+ const __u64 handled;
+ const __u64 allowed;
+ const mode_t open_mode;
+ /*
+ * TCGETS is used as a characteristic device-specific IOCTL command.
+ * The logic is the same for other IOCTL commands as well.
+ */
+ const int expected_tcgets_result; /* terminal device IOCTL */
+ /*
+ * FIONREAD is implemented in fs/ioctl.c for regular files,
+ * but we do not blanket-permit it for devices.
+ */
+ const int expected_fionread_result;
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, handled_i_allowed_none) {
+ /* clang-format on */
+ .handled = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+ .allowed = 0,
+ .open_mode = O_RDWR,
+ .expected_tcgets_result = EACCES,
+ .expected_fionread_result = EACCES,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, handled_i_allowed_i) {
+ /* clang-format on */
+ .handled = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+ .allowed = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+ .open_mode = O_RDWR,
+ .expected_tcgets_result = 0,
+ .expected_fionread_result = 0,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, unhandled) {
+ /* clang-format on */
+ .handled = LANDLOCK_ACCESS_FS_EXECUTE,
+ .allowed = LANDLOCK_ACCESS_FS_EXECUTE,
+ .open_mode = O_RDWR,
+ .expected_tcgets_result = 0,
+ .expected_fionread_result = 0,
+};
+
+static int test_fioqsize_ioctl(int fd)
+{
+ size_t sz;
+
+ if (ioctl(fd, FIOQSIZE, &sz) < 0)
+ return errno;
+ return 0;
+}
+
+static int test_tcgets_ioctl(int fd)
+{
+ struct termios info;
+
+ if (ioctl(fd, TCGETS, &info) < 0)
+ return errno;
+ return 0;
+}
+
+TEST_F_FORK(ioctl, handle_dir_access_file)
+{
+ const int flag = 0;
+ const struct rule rules[] = {
+ {
+ .path = "/dev",
+ .access = variant->allowed,
+ },
+ {},
+ };
+ int file_fd, ruleset_fd;
+
+ /* Enables Landlock. */
+ ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ ASSERT_EQ(0, close(ruleset_fd));
+
+ file_fd = open("/dev/tty", variant->open_mode);
+ ASSERT_LE(0, file_fd);
+
+ /* Checks that IOCTL commands return the expected errors. */
+ EXPECT_EQ(variant->expected_tcgets_result, test_tcgets_ioctl(file_fd));
+ EXPECT_EQ(variant->expected_fionread_result,
+ test_fionread_ioctl(file_fd));
+
+ /* Checks that unrestrictable commands are unrestricted. */
+ EXPECT_EQ(0, ioctl(file_fd, FIOCLEX));
+ EXPECT_EQ(0, ioctl(file_fd, FIONCLEX));
+ EXPECT_EQ(0, ioctl(file_fd, FIONBIO, &flag));
+ EXPECT_EQ(0, ioctl(file_fd, FIOASYNC, &flag));
+ EXPECT_EQ(ENOTTY, test_fioqsize_ioctl(file_fd));
+
+ ASSERT_EQ(0, close(file_fd));
+}
+
+TEST_F_FORK(ioctl, handle_dir_access_dir)
+{
+ const int flag = 0;
+ const struct rule rules[] = {
+ {
+ .path = "/dev",
+ .access = variant->allowed,
+ },
+ {},
+ };
+ int dir_fd, ruleset_fd;
+
+ /* Enables Landlock. */
+ ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ ASSERT_EQ(0, close(ruleset_fd));
+
+ /*
+ * Ignore variant->open_mode for this test, as we intend to open a
+ * directory. If the directory can not be opened, the variant is
+ * infeasible to test with an opened directory.
+ */
+ dir_fd = open("/dev", O_RDONLY);
+ if (dir_fd < 0)
+ return;
+
+ /*
+ * Checks that IOCTL commands return the expected errors.
+ * We do not use the expected values from the fixture here.
+ *
+ * When using IOCTL on a directory, no Landlock restrictions apply.
+ * TCGETS will fail anyway because it is not invoked on a TTY device.
+ */
+ EXPECT_EQ(ENOTTY, test_tcgets_ioctl(dir_fd));
+ EXPECT_EQ(0, test_fionread_ioctl(dir_fd));
+
+ /* Checks that unrestrictable commands are unrestricted. */
+ EXPECT_EQ(0, ioctl(dir_fd, FIOCLEX));
+ EXPECT_EQ(0, ioctl(dir_fd, FIONCLEX));
+ EXPECT_EQ(0, ioctl(dir_fd, FIONBIO, &flag));
+ EXPECT_EQ(0, ioctl(dir_fd, FIOASYNC, &flag));
+ EXPECT_EQ(0, test_fioqsize_ioctl(dir_fd));
+
+ ASSERT_EQ(0, close(dir_fd));
+}
+
+TEST_F_FORK(ioctl, handle_file_access_file)
+{
+ const int flag = 0;
+ const struct rule rules[] = {
+ {
+ .path = "/dev/tty0",
+ .access = variant->allowed,
+ },
+ {},
+ };
+ int file_fd, ruleset_fd;
+
+ if (variant->allowed & LANDLOCK_ACCESS_FS_READ_DIR) {
+ SKIP(return, "LANDLOCK_ACCESS_FS_READ_DIR "
+ "can not be granted on files");
+ }
+
+ /* Enables Landlock. */
+ ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ ASSERT_EQ(0, close(ruleset_fd));
+
+ file_fd = open("/dev/tty0", variant->open_mode);
+ ASSERT_LE(0, file_fd)
+ {
+ TH_LOG("Failed to open /dev/tty0: %s", strerror(errno));
+ }
+
+ /* Checks that IOCTL commands return the expected errors. */
+ EXPECT_EQ(variant->expected_tcgets_result, test_tcgets_ioctl(file_fd));
+ EXPECT_EQ(variant->expected_fionread_result,
+ test_fionread_ioctl(file_fd));
+
+ /* Checks that unrestrictable commands are unrestricted. */
+ EXPECT_EQ(0, ioctl(file_fd, FIOCLEX));
+ EXPECT_EQ(0, ioctl(file_fd, FIONCLEX));
+ EXPECT_EQ(0, ioctl(file_fd, FIONBIO, &flag));
+ EXPECT_EQ(0, ioctl(file_fd, FIOASYNC, &flag));
+ EXPECT_EQ(ENOTTY, test_fioqsize_ioctl(file_fd));
+
+ ASSERT_EQ(0, close(file_fd));
+}
+
/* clang-format off */
FIXTURE(layout1_bind) {};
/* clang-format on */
--
2.44.0.396.g6e790dbe36-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v11 4/9] selftests/landlock: Test IOCTL with memfds
2024-03-22 15:09 [PATCH v11 0/9] Landlock: IOCTL support Günther Noack
` (2 preceding siblings ...)
2024-03-22 15:09 ` [PATCH v11 3/9] selftests/landlock: Test IOCTL support Günther Noack
@ 2024-03-22 15:09 ` Günther Noack
2024-03-22 15:09 ` [PATCH v11 5/9] selftests/landlock: Test ioctl(2) and ftruncate(2) with open(O_PATH) Günther Noack
` (4 subsequent siblings)
8 siblings, 0 replies; 12+ messages in thread
From: Günther Noack @ 2024-03-22 15:09 UTC (permalink / raw)
To: linux-security-module, Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Günther Noack
Because the LANDLOCK_ACCESS_FS_IOCTL_DEV right is associated with the
opened file during open(2), IOCTLs are supposed to work with files
which are opened by means other than open(2).
Signed-off-by: Günther Noack <gnoack@google.com>
---
tools/testing/selftests/landlock/fs_test.c | 36 ++++++++++++++++------
1 file changed, 27 insertions(+), 9 deletions(-)
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 22229fe3e403..32a77757462b 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -3850,20 +3850,38 @@ static int test_fs_ioc_getflags_ioctl(int fd)
return 0;
}
-TEST(memfd_ftruncate)
+TEST(memfd_ftruncate_and_ioctl)
{
- int fd;
-
- fd = memfd_create("name", MFD_CLOEXEC);
- ASSERT_LE(0, fd);
+ const struct landlock_ruleset_attr attr = {
+ .handled_access_fs = ACCESS_ALL,
+ };
+ int ruleset_fd, fd, i;
/*
- * Checks that ftruncate is permitted on file descriptors that are
- * created in ways other than open(2).
+ * We exercise the same test both with and without Landlock enabled, to
+ * ensure that it behaves the same in both cases.
*/
- EXPECT_EQ(0, test_ftruncate(fd));
+ for (i = 0; i < 2; i++) {
+ /* Creates a new memfd. */
+ fd = memfd_create("name", MFD_CLOEXEC);
+ ASSERT_LE(0, fd);
- ASSERT_EQ(0, close(fd));
+ /*
+ * Checks that operations associated with the opened file
+ * (ftruncate, ioctl) are permitted on file descriptors that are
+ * created in ways other than open(2).
+ */
+ EXPECT_EQ(0, test_ftruncate(fd));
+ EXPECT_EQ(0, test_fs_ioc_getflags_ioctl(fd));
+
+ ASSERT_EQ(0, close(fd));
+
+ /* Enables Landlock. */
+ ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ ASSERT_EQ(0, close(ruleset_fd));
+ }
}
static int test_fionread_ioctl(int fd)
--
2.44.0.396.g6e790dbe36-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v11 5/9] selftests/landlock: Test ioctl(2) and ftruncate(2) with open(O_PATH)
2024-03-22 15:09 [PATCH v11 0/9] Landlock: IOCTL support Günther Noack
` (3 preceding siblings ...)
2024-03-22 15:09 ` [PATCH v11 4/9] selftests/landlock: Test IOCTL with memfds Günther Noack
@ 2024-03-22 15:09 ` Günther Noack
2024-03-22 15:09 ` [PATCH v11 6/9] selftests/landlock: Test IOCTLs on named pipes Günther Noack
` (3 subsequent siblings)
8 siblings, 0 replies; 12+ messages in thread
From: Günther Noack @ 2024-03-22 15:09 UTC (permalink / raw)
To: linux-security-module, Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Günther Noack
ioctl(2) and ftruncate(2) operations on files opened with O_PATH
should always return EBADF, independent of the
LANDLOCK_ACCESS_FS_TRUNCATE and LANDLOCK_ACCESS_FS_IOCTL_DEV access
rights in that file hierarchy.
Suggested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack@google.com>
---
tools/testing/selftests/landlock/fs_test.c | 40 ++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 32a77757462b..dde4673e2df4 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -3893,6 +3893,46 @@ static int test_fionread_ioctl(int fd)
return 0;
}
+TEST_F_FORK(layout1, o_path_ftruncate_and_ioctl)
+{
+ const struct landlock_ruleset_attr attr = {
+ .handled_access_fs = ACCESS_ALL,
+ };
+ int ruleset_fd, fd;
+
+ /*
+ * Checks that for files opened with O_PATH, both ioctl(2) and
+ * ftruncate(2) yield EBADF, as it is documented in open(2) for the
+ * O_PATH flag.
+ */
+ fd = open(dir_s1d1, O_PATH | O_CLOEXEC);
+ ASSERT_LE(0, fd);
+
+ EXPECT_EQ(EBADF, test_ftruncate(fd));
+ EXPECT_EQ(EBADF, test_fs_ioc_getflags_ioctl(fd));
+
+ ASSERT_EQ(0, close(fd));
+
+ /* Enables Landlock. */
+ ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ ASSERT_EQ(0, close(ruleset_fd));
+
+ /*
+ * Checks that after enabling Landlock,
+ * - the file can still be opened with O_PATH
+ * - both ioctl and truncate still yield EBADF (not EACCES).
+ */
+ fd = open(dir_s1d1, O_PATH | O_CLOEXEC);
+ ASSERT_LE(0, fd);
+
+ EXPECT_EQ(EBADF, test_ftruncate(fd));
+ EXPECT_EQ(EBADF, test_fs_ioc_getflags_ioctl(fd));
+
+ ASSERT_EQ(0, close(fd));
+}
+
/* clang-format off */
FIXTURE(ioctl) {};
--
2.44.0.396.g6e790dbe36-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v11 6/9] selftests/landlock: Test IOCTLs on named pipes
2024-03-22 15:09 [PATCH v11 0/9] Landlock: IOCTL support Günther Noack
` (4 preceding siblings ...)
2024-03-22 15:09 ` [PATCH v11 5/9] selftests/landlock: Test ioctl(2) and ftruncate(2) with open(O_PATH) Günther Noack
@ 2024-03-22 15:09 ` Günther Noack
2024-03-22 15:10 ` [PATCH v11 7/9] selftests/landlock: Check IOCTL restrictions for named UNIX domain sockets Günther Noack
` (2 subsequent siblings)
8 siblings, 0 replies; 12+ messages in thread
From: Günther Noack @ 2024-03-22 15:09 UTC (permalink / raw)
To: linux-security-module, Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Günther Noack
Named pipes should behave like pipes created with pipe(2),
so we don't want to restrict IOCTLs on them.
Suggested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack@google.com>
---
tools/testing/selftests/landlock/fs_test.c | 43 ++++++++++++++++++++++
1 file changed, 43 insertions(+)
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index dde4673e2df4..d3aaa343f6e4 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -3933,6 +3933,49 @@ TEST_F_FORK(layout1, o_path_ftruncate_and_ioctl)
ASSERT_EQ(0, close(fd));
}
+/*
+ * Named pipes are not governed by the LANDLOCK_ACCESS_FS_IOCTL_DEV right,
+ * because they are not character or block devices.
+ */
+TEST_F_FORK(layout1, named_pipe_ioctl)
+{
+ pid_t child_pid;
+ int fd, ruleset_fd;
+ const char *const path = file1_s1d1;
+ const struct landlock_ruleset_attr attr = {
+ .handled_access_fs = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+ };
+
+ ASSERT_EQ(0, unlink(path));
+ ASSERT_EQ(0, mkfifo(path, 0600));
+
+ /* Enables Landlock. */
+ ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ ASSERT_EQ(0, close(ruleset_fd));
+
+ /* The child process opens the pipe for writing. */
+ child_pid = fork();
+ ASSERT_NE(-1, child_pid);
+ if (child_pid == 0) {
+ fd = open(path, O_WRONLY);
+ close(fd);
+ exit(0);
+ }
+
+ fd = open(path, O_RDONLY);
+ ASSERT_LE(0, fd);
+
+ /* FIONREAD is implemented by pipefifo_fops. */
+ EXPECT_EQ(0, test_fionread_ioctl(fd));
+
+ ASSERT_EQ(0, close(fd));
+ ASSERT_EQ(0, unlink(path));
+
+ ASSERT_EQ(child_pid, waitpid(child_pid, NULL, 0));
+}
+
/* clang-format off */
FIXTURE(ioctl) {};
--
2.44.0.396.g6e790dbe36-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v11 7/9] selftests/landlock: Check IOCTL restrictions for named UNIX domain sockets
2024-03-22 15:09 [PATCH v11 0/9] Landlock: IOCTL support Günther Noack
` (5 preceding siblings ...)
2024-03-22 15:09 ` [PATCH v11 6/9] selftests/landlock: Test IOCTLs on named pipes Günther Noack
@ 2024-03-22 15:10 ` Günther Noack
2024-03-22 15:10 ` [PATCH v11 8/9] samples/landlock: Add support for LANDLOCK_ACCESS_FS_IOCTL_DEV Günther Noack
2024-03-22 15:10 ` [PATCH v11 9/9] landlock: Document IOCTL support Günther Noack
8 siblings, 0 replies; 12+ messages in thread
From: Günther Noack @ 2024-03-22 15:10 UTC (permalink / raw)
To: linux-security-module, Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Günther Noack
Suggested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack@google.com>
---
tools/testing/selftests/landlock/fs_test.c | 51 ++++++++++++++++++++++
1 file changed, 51 insertions(+)
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index d3aaa343f6e4..2ade195bde56 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -20,8 +20,10 @@
#include <sys/mount.h>
#include <sys/prctl.h>
#include <sys/sendfile.h>
+#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
+#include <sys/un.h>
#include <sys/vfs.h>
#include <unistd.h>
@@ -3976,6 +3978,55 @@ TEST_F_FORK(layout1, named_pipe_ioctl)
ASSERT_EQ(child_pid, waitpid(child_pid, NULL, 0));
}
+/* For named UNIX domain sockets, no IOCTL restrictions apply. */
+TEST_F_FORK(layout1, named_unix_domain_socket_ioctl)
+{
+ const char *const path = file1_s1d1;
+ int srv_fd, cli_fd, ruleset_fd;
+ socklen_t size;
+ struct sockaddr_un srv_un, cli_un;
+ const struct landlock_ruleset_attr attr = {
+ .handled_access_fs = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+ };
+
+ /* Sets up a server */
+ srv_un.sun_family = AF_UNIX;
+ strncpy(srv_un.sun_path, path, sizeof(srv_un.sun_path));
+
+ ASSERT_EQ(0, unlink(path));
+ ASSERT_LE(0, (srv_fd = socket(AF_UNIX, SOCK_STREAM, 0)));
+
+ size = offsetof(struct sockaddr_un, sun_path) + strlen(srv_un.sun_path);
+ ASSERT_EQ(0, bind(srv_fd, (struct sockaddr *)&srv_un, size));
+ ASSERT_EQ(0, listen(srv_fd, 10 /* qlen */));
+
+ /* Enables Landlock. */
+ ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+ enforce_ruleset(_metadata, ruleset_fd);
+ ASSERT_EQ(0, close(ruleset_fd));
+
+ /* Sets up a client connection to it */
+ cli_un.sun_family = AF_UNIX;
+
+ ASSERT_LE(0, (cli_fd = socket(AF_UNIX, SOCK_STREAM, 0)));
+
+ size = offsetof(struct sockaddr_un, sun_path) + strlen(cli_un.sun_path);
+ ASSERT_EQ(0, bind(cli_fd, (struct sockaddr *)&cli_un, size));
+
+ bzero(&cli_un, sizeof(cli_un));
+ cli_un.sun_family = AF_UNIX;
+ strncpy(cli_un.sun_path, path, sizeof(cli_un.sun_path));
+ size = offsetof(struct sockaddr_un, sun_path) + strlen(cli_un.sun_path);
+
+ ASSERT_EQ(0, connect(cli_fd, (struct sockaddr *)&cli_un, size));
+
+ /* FIONREAD and other IOCTLs should not be forbidden. */
+ EXPECT_EQ(0, test_fionread_ioctl(cli_fd));
+
+ ASSERT_EQ(0, close(cli_fd));
+}
+
/* clang-format off */
FIXTURE(ioctl) {};
--
2.44.0.396.g6e790dbe36-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v11 8/9] samples/landlock: Add support for LANDLOCK_ACCESS_FS_IOCTL_DEV
2024-03-22 15:09 [PATCH v11 0/9] Landlock: IOCTL support Günther Noack
` (6 preceding siblings ...)
2024-03-22 15:10 ` [PATCH v11 7/9] selftests/landlock: Check IOCTL restrictions for named UNIX domain sockets Günther Noack
@ 2024-03-22 15:10 ` Günther Noack
2024-03-22 15:10 ` [PATCH v11 9/9] landlock: Document IOCTL support Günther Noack
8 siblings, 0 replies; 12+ messages in thread
From: Günther Noack @ 2024-03-22 15:10 UTC (permalink / raw)
To: linux-security-module, Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Günther Noack
Add IOCTL support to the Landlock sample tool.
The IOCTL right is grouped with the read-write rights in the sample
tool, as some IOCTL requests provide features that mutate state.
Signed-off-by: Günther Noack <gnoack@google.com>
---
samples/landlock/sandboxer.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index 32e930c853bb..997f774e88ae 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -81,7 +81,8 @@ static int parse_path(char *env_path, const char ***const path_list)
LANDLOCK_ACCESS_FS_EXECUTE | \
LANDLOCK_ACCESS_FS_WRITE_FILE | \
LANDLOCK_ACCESS_FS_READ_FILE | \
- LANDLOCK_ACCESS_FS_TRUNCATE)
+ LANDLOCK_ACCESS_FS_TRUNCATE | \
+ LANDLOCK_ACCESS_FS_IOCTL_DEV)
/* clang-format on */
@@ -201,11 +202,12 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
LANDLOCK_ACCESS_FS_MAKE_BLOCK | \
LANDLOCK_ACCESS_FS_MAKE_SYM | \
LANDLOCK_ACCESS_FS_REFER | \
- LANDLOCK_ACCESS_FS_TRUNCATE)
+ LANDLOCK_ACCESS_FS_TRUNCATE | \
+ LANDLOCK_ACCESS_FS_IOCTL_DEV)
/* clang-format on */
-#define LANDLOCK_ABI_LAST 4
+#define LANDLOCK_ABI_LAST 5
int main(const int argc, char *const argv[], char *const *const envp)
{
@@ -319,6 +321,11 @@ int main(const int argc, char *const argv[], char *const *const envp)
ruleset_attr.handled_access_net &=
~(LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP);
+ __attribute__((fallthrough));
+ case 4:
+ /* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */
+ ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV;
+
fprintf(stderr,
"Hint: You should update the running kernel "
"to leverage Landlock features "
--
2.44.0.396.g6e790dbe36-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v11 9/9] landlock: Document IOCTL support
2024-03-22 15:09 [PATCH v11 0/9] Landlock: IOCTL support Günther Noack
` (7 preceding siblings ...)
2024-03-22 15:10 ` [PATCH v11 8/9] samples/landlock: Add support for LANDLOCK_ACCESS_FS_IOCTL_DEV Günther Noack
@ 2024-03-22 15:10 ` Günther Noack
8 siblings, 0 replies; 12+ messages in thread
From: Günther Noack @ 2024-03-22 15:10 UTC (permalink / raw)
To: linux-security-module, Mickaël Salaün
Cc: Jeff Xu, Jorge Lucangeli Obes, Allen Webb, Dmitry Torokhov,
Paul Moore, Konstantin Meskhidze, Matt Bobrowski, linux-fsdevel,
Günther Noack
In the paragraph above the fallback logic, use the shorter phrasing
from the landlock(7) man page.
Signed-off-by: Günther Noack <gnoack@google.com>
---
Documentation/userspace-api/landlock.rst | 76 +++++++++++++++++++-----
1 file changed, 61 insertions(+), 15 deletions(-)
diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
index 9dd636aaa829..145bd869c684 100644
--- a/Documentation/userspace-api/landlock.rst
+++ b/Documentation/userspace-api/landlock.rst
@@ -76,7 +76,8 @@ to be explicit about the denied-by-default access rights.
LANDLOCK_ACCESS_FS_MAKE_BLOCK |
LANDLOCK_ACCESS_FS_MAKE_SYM |
LANDLOCK_ACCESS_FS_REFER |
- LANDLOCK_ACCESS_FS_TRUNCATE,
+ LANDLOCK_ACCESS_FS_TRUNCATE |
+ LANDLOCK_ACCESS_FS_IOCTL_DEV,
.handled_access_net =
LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP,
@@ -85,10 +86,10 @@ to be explicit about the denied-by-default access rights.
Because we may not know on which kernel version an application will be
executed, it is safer to follow a best-effort security approach. Indeed, we
should try to protect users as much as possible whatever the kernel they are
-using. To avoid binary enforcement (i.e. either all security features or
-none), we can leverage a dedicated Landlock command to get the current version
-of the Landlock ABI and adapt the handled accesses. Let's check if we should
-remove access rights which are only supported in higher versions of the ABI.
+using.
+
+To be compatible with older Linux versions, we detect the available Landlock ABI
+version, and only use the available subset of access rights:
.. code-block:: c
@@ -114,6 +115,10 @@ remove access rights which are only supported in higher versions of the ABI.
ruleset_attr.handled_access_net &=
~(LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP);
+ __attribute__((fallthrough));
+ case 4:
+ /* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */
+ ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV;
}
This enables to create an inclusive ruleset that will contain our rules.
@@ -225,6 +230,7 @@ access rights per directory enables to change the location of such directory
without relying on the destination directory access rights (except those that
are required for this operation, see ``LANDLOCK_ACCESS_FS_REFER``
documentation).
+
Having self-sufficient hierarchies also helps to tighten the required access
rights to the minimal set of data. This also helps avoid sinkhole directories,
i.e. directories where data can be linked to but not linked from. However,
@@ -318,18 +324,26 @@ It should also be noted that truncating files does not require the
system call, this can also be done through :manpage:`open(2)` with the flags
``O_RDONLY | O_TRUNC``.
-When opening a file, the availability of the ``LANDLOCK_ACCESS_FS_TRUNCATE``
-right is associated with the newly created file descriptor and will be used for
-subsequent truncation attempts using :manpage:`ftruncate(2)`. The behavior is
-similar to opening a file for reading or writing, where permissions are checked
-during :manpage:`open(2)`, but not during the subsequent :manpage:`read(2)` and
+The truncate right is associated with the opened file (see below).
+
+Rights associated with file descriptors
+---------------------------------------
+
+When opening a file, the availability of the ``LANDLOCK_ACCESS_FS_TRUNCATE`` and
+``LANDLOCK_ACCESS_FS_IOCTL_DEV`` rights is associated with the newly created
+file descriptor and will be used for subsequent truncation and ioctl attempts
+using :manpage:`ftruncate(2)` and :manpage:`ioctl(2)`. The behavior is similar
+to opening a file for reading or writing, where permissions are checked during
+:manpage:`open(2)`, but not during the subsequent :manpage:`read(2)` and
:manpage:`write(2)` calls.
-As a consequence, it is possible to have multiple open file descriptors for the
-same file, where one grants the right to truncate the file and the other does
-not. It is also possible to pass such file descriptors between processes,
-keeping their Landlock properties, even when these processes do not have an
-enforced Landlock ruleset.
+As a consequence, it is possible that a process has multiple open file
+descriptors referring to the same file, but Landlock enforces different things
+when operating with these file descriptors. This can happen when a Landlock
+ruleset gets enforced and the process keeps file descriptors which were opened
+both before and after the enforcement. It is also possible to pass such file
+descriptors between processes, keeping their Landlock properties, even when some
+of the involved processes do not have an enforced Landlock ruleset.
Compatibility
=============
@@ -458,6 +472,28 @@ Memory usage
Kernel memory allocated to create rulesets is accounted and can be restricted
by the Documentation/admin-guide/cgroup-v1/memory.rst.
+IOCTL support
+-------------
+
+The ``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right restricts the use of
+:manpage:`ioctl(2)`, but it only applies to *newly opened* device files. This
+means specifically that pre-existing file descriptors like stdin, stdout and
+stderr are unaffected.
+
+Users should be aware that TTY devices have traditionally permitted to control
+other processes on the same TTY through the ``TIOCSTI`` and ``TIOCLINUX`` IOCTL
+commands. Both of these require ``CAP_SYS_ADMIN`` on modern Linux systems, but
+the behavior is configurable for ``TIOCSTI``.
+
+On older systems, it is therefore recommended to close inherited TTY file
+descriptors, or to reopen them from ``/proc/self/fd/*`` without the
+``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right, if possible.
+
+Landlock's IOCTL support is coarse-grained at the moment, but may become more
+fine-grained in the future. Until then, users are advised to establish the
+guarantees that they need through the file hierarchy, by only allowing the
+``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right on files where it is really required.
+
Previous limitations
====================
@@ -495,6 +531,16 @@ bind and connect actions to only a set of allowed ports thanks to the new
``LANDLOCK_ACCESS_NET_BIND_TCP`` and ``LANDLOCK_ACCESS_NET_CONNECT_TCP``
access rights.
+IOCTL (ABI < 5)
+---------------
+
+IOCTL operations could not be denied before the fifth Landlock ABI, so
+:manpage:`ioctl(2)` is always allowed when using a kernel that only supports an
+earlier ABI.
+
+Starting with the Landlock ABI version 5, it is possible to restrict the use of
+:manpage:`ioctl(2)` using the new ``LANDLOCK_ACCESS_FS_IOCTL_DEV`` access right.
+
.. _kernel_support:
Kernel support
--
2.44.0.396.g6e790dbe36-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread