* [PATCH 0/2 RESEND] POSIX-compliant version of fchmodat with flag argument
@ 2012-01-13 1:53 Andrew Ayer
2012-01-13 1:53 ` [PATCH 1/2] vfs: Add fchmodat4 syscall: " Andrew Ayer
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Andrew Ayer @ 2012-01-13 1:53 UTC (permalink / raw)
To: Alexander Viro; +Cc: linux-fsdevel, linux-kernel
Hi,
The below patches implement a 4 argument version of fchmodat (fchmodat4)
that has a flag argument, as specified by POSIX. This is needed to
implement a proper glibc wrapper.
fchmodat4 supports the same two flags as fchownat: AT_SYMLINK_NOFOLLOW
and AT_EMPTY_PATH.
Besides the POSIX-compliance, this patch will make it possible to
ensure, in a race-free way, that you do not follow symlinks when
chmodding. Previously, you could open a file with O_NOFOLLOW and fchmod
it, but this only worked if you had read or write permissions on the
file. Now you can open the file with O_PATH|O_NOFOLLOW and do fchmodat
with AT_EMPTY_PATH.
Could this patch be applied? Any feedback is welcome.
Cheers,
Andrew
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH 1/2] vfs: Add fchmodat4 syscall: fchmodat with flag argument 2012-01-13 1:53 [PATCH 0/2 RESEND] POSIX-compliant version of fchmodat with flag argument Andrew Ayer @ 2012-01-13 1:53 ` Andrew Ayer 2014-01-21 7:30 ` Florian Weimer 2012-01-13 1:53 ` [PATCH 2/2] x86: Hook up new fchmodat4 syscall Andrew Ayer 2012-09-18 20:39 ` [PATCH 0/2 RESEND] POSIX-compliant version of fchmodat with flag argument Kenny Root 2 siblings, 1 reply; 7+ messages in thread From: Andrew Ayer @ 2012-01-13 1:53 UTC (permalink / raw) To: Alexander Viro; +Cc: linux-fsdevel, linux-kernel This adds a 4 argument version of fchmodat (fchmodat4) that supports a flag argument, as specified by POSIX. It supports the same two flags as fchownat: AT_SYMLINK_NOFOLLOW and AT_EMPTY_PATH. Signed-off-by: Andrew Ayer <agwa@andrewayer.name> --- fs/open.c | 21 +++++++++++++++++++-- include/linux/syscalls.h | 2 ++ 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/fs/open.c b/fs/open.c index 77becc0..4f087e7 100644 --- a/fs/open.c +++ b/fs/open.c @@ -452,6 +452,9 @@ static int chmod_common(struct path *path, umode_t mode) struct iattr newattrs; int error; + if (S_ISLNK(inode->i_mode)) + return -EOPNOTSUPP; + error = mnt_want_write(path->mnt); if (error) return error; @@ -484,10 +487,24 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { + return sys_fchmodat4(dfd, filename, mode, 0); +} + +SYSCALL_DEFINE4(fchmodat4, int, dfd, const char __user *, filename, + umode_t, mode, int, flag) +{ struct path path; int error; + int lookup_flags; + + if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) + return -EINVAL; - error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path); + lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW; + if (flag & AT_EMPTY_PATH) + lookup_flags |= LOOKUP_EMPTY; + + error = user_path_at(dfd, filename, lookup_flags, &path); if (!error) { error = chmod_common(&path, mode); path_put(&path); @@ -497,7 +514,7 @@ SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) { - return sys_fchmodat(AT_FDCWD, filename, mode); + return sys_fchmodat4(AT_FDCWD, filename, mode, 0); } static int chown_common(struct path *path, uid_t user, gid_t group) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 515669f..4834904 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -770,6 +770,8 @@ asmlinkage long sys_futimesat(int dfd, const char __user *filename, asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode); asmlinkage long sys_fchmodat(int dfd, const char __user * filename, umode_t mode); +asmlinkage long sys_fchmodat4(int dfd, const char __user * filename, + umode_t mode, int flag); asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group, int flag); asmlinkage long sys_openat(int dfd, const char __user *filename, int flags, -- 1.7.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] vfs: Add fchmodat4 syscall: fchmodat with flag argument 2012-01-13 1:53 ` [PATCH 1/2] vfs: Add fchmodat4 syscall: " Andrew Ayer @ 2014-01-21 7:30 ` Florian Weimer 2014-01-21 18:57 ` Andrew Ayer 0 siblings, 1 reply; 7+ messages in thread From: Florian Weimer @ 2014-01-21 7:30 UTC (permalink / raw) To: Andrew Ayer, Alexander Viro; +Cc: linux-fsdevel, linux-kernel On 01/13/2012 02:53 AM, Andrew Ayer wrote: > This adds a 4 argument version of fchmodat (fchmodat4) that > supports a flag argument, as specified by POSIX. It supports > the same two flags as fchownat: AT_SYMLINK_NOFOLLOW and AT_EMPTY_PATH. I don't think it's possible to emulate AT_EMPTY_PATH in user space, so I wonder if this could be applied, and if not, why. Thanks. -- Florian Weimer / Red Hat Product Security Team ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] vfs: Add fchmodat4 syscall: fchmodat with flag argument 2014-01-21 7:30 ` Florian Weimer @ 2014-01-21 18:57 ` Andrew Ayer 2014-01-21 18:58 ` [PATCH] vfs: Add version of " Andrew Ayer 0 siblings, 1 reply; 7+ messages in thread From: Andrew Ayer @ 2014-01-21 18:57 UTC (permalink / raw) To: Florian Weimer, Alexander Viro; +Cc: linux-fsdevel, linux-kernel On Tue, 21 Jan 2014 08:30:16 +0100 Florian Weimer <fweimer@redhat.com> wrote: > On 01/13/2012 02:53 AM, Andrew Ayer wrote: > > This adds a 4 argument version of fchmodat (fchmodat4) that > > supports a flag argument, as specified by POSIX. It supports > > the same two flags as fchownat: AT_SYMLINK_NOFOLLOW and AT_EMPTY_PATH. > > I don't think it's possible to emulate AT_EMPTY_PATH in user space, so I > wonder if this could be applied, and if not, why. Thanks. The original patch no longer applies because there were some minor changes to fs/open.c. I'll fix up the patch and send it in. I too would very much like to see this applied, or to know why it can't be. Thanks, Andrew ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] vfs: Add version of fchmodat with flag argument 2014-01-21 18:57 ` Andrew Ayer @ 2014-01-21 18:58 ` Andrew Ayer 0 siblings, 0 replies; 7+ messages in thread From: Andrew Ayer @ 2014-01-21 18:58 UTC (permalink / raw) To: viro; +Cc: linux-fsdevel, linux-kernel, fweimer This adds a 4 argument version of fchmodat (fchmodat4) that supports a flag argument, as specified by POSIX. It supports the same two flags as fchownat: AT_SYMLINK_NOFOLLOW and AT_EMPTY_PATH. Signed-off-by: Andrew Ayer <agwa@andrewayer.name> --- fs/open.c | 23 ++++++++++++++++++++--- include/linux/syscalls.h | 2 ++ 2 files changed, 22 insertions(+), 3 deletions(-) diff --git a/fs/open.c b/fs/open.c index 4b3e1ed..6f661f9 100644 --- a/fs/open.c +++ b/fs/open.c @@ -469,6 +469,9 @@ static int chmod_common(struct path *path, umode_t mode) struct iattr newattrs; int error; + if (S_ISLNK(inode->i_mode)) + return -EOPNOTSUPP; + error = mnt_want_write(path->mnt); if (error) return error; @@ -506,9 +509,22 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { + return sys_fchmodat4(dfd, filename, mode, 0); +} + +SYSCALL_DEFINE4(fchmodat4, int, dfd, const char __user *, filename, + umode_t, mode, int, flag) +{ struct path path; - int error; - unsigned int lookup_flags = LOOKUP_FOLLOW; + int error = -EINVAL; + unsigned int lookup_flags; + + if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) + goto out; + + lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW; + if (flag & AT_EMPTY_PATH) + lookup_flags |= LOOKUP_EMPTY; retry: error = user_path_at(dfd, filename, lookup_flags, &path); if (!error) { @@ -519,12 +535,13 @@ retry: goto retry; } } +out: return error; } SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) { - return sys_fchmodat(AT_FDCWD, filename, mode); + return sys_fchmodat4(AT_FDCWD, filename, mode, 0); } static int chown_common(struct path *path, uid_t user, gid_t group) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 40ed9e9..32811df 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -747,6 +747,8 @@ asmlinkage long sys_futimesat(int dfd, const char __user *filename, asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode); asmlinkage long sys_fchmodat(int dfd, const char __user * filename, umode_t mode); +asmlinkage long sys_fchmodat4(int dfd, const char __user *filename, + umode_t mode, int flag); asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group, int flag); asmlinkage long sys_openat(int dfd, const char __user *filename, int flags, -- 1.7.10.4 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH 2/2] x86: Hook up new fchmodat4 syscall 2012-01-13 1:53 [PATCH 0/2 RESEND] POSIX-compliant version of fchmodat with flag argument Andrew Ayer 2012-01-13 1:53 ` [PATCH 1/2] vfs: Add fchmodat4 syscall: " Andrew Ayer @ 2012-01-13 1:53 ` Andrew Ayer 2012-09-18 20:39 ` [PATCH 0/2 RESEND] POSIX-compliant version of fchmodat with flag argument Kenny Root 2 siblings, 0 replies; 7+ messages in thread From: Andrew Ayer @ 2012-01-13 1:53 UTC (permalink / raw) To: Alexander Viro; +Cc: linux-fsdevel, linux-kernel Signed-off-by: Andrew Ayer <agwa@andrewayer.name> --- arch/x86/ia32/ia32entry.S | 1 + arch/x86/include/asm/unistd_32.h | 3 ++- arch/x86/include/asm/unistd_64.h | 2 ++ arch/x86/kernel/syscall_table_32.S | 1 + 4 files changed, 6 insertions(+), 1 deletions(-) diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index 3e27456..f026e9f 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -847,4 +847,5 @@ ia32_sys_call_table: .quad sys_setns .quad compat_sys_process_vm_readv .quad compat_sys_process_vm_writev + .quad sys_fchmodat4 ia32_syscall_end: diff --git a/arch/x86/include/asm/unistd_32.h b/arch/x86/include/asm/unistd_32.h index 599c77d..112b299 100644 --- a/arch/x86/include/asm/unistd_32.h +++ b/arch/x86/include/asm/unistd_32.h @@ -354,10 +354,11 @@ #define __NR_setns 346 #define __NR_process_vm_readv 347 #define __NR_process_vm_writev 348 +#define __NR_fchmodat4 349 #ifdef __KERNEL__ -#define NR_syscalls 349 +#define NR_syscalls 350 #define __ARCH_WANT_IPC_PARSE_VERSION #define __ARCH_WANT_OLD_READDIR diff --git a/arch/x86/include/asm/unistd_64.h b/arch/x86/include/asm/unistd_64.h index 0431f19..21564f9 100644 --- a/arch/x86/include/asm/unistd_64.h +++ b/arch/x86/include/asm/unistd_64.h @@ -686,6 +686,8 @@ __SYSCALL(__NR_getcpu, sys_getcpu) __SYSCALL(__NR_process_vm_readv, sys_process_vm_readv) #define __NR_process_vm_writev 311 __SYSCALL(__NR_process_vm_writev, sys_process_vm_writev) +#define __NR_fchmodat4 312 +__SYSCALL(__NR_fchmodat4, sys_fchmodat4) #ifndef __NO_STUBS #define __ARCH_WANT_OLD_READDIR diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S index 9a0e312..bff82a6 100644 --- a/arch/x86/kernel/syscall_table_32.S +++ b/arch/x86/kernel/syscall_table_32.S @@ -348,3 +348,4 @@ ENTRY(sys_call_table) .long sys_setns .long sys_process_vm_readv .long sys_process_vm_writev + .long sys_fchmodat4 -- 1.7.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 0/2 RESEND] POSIX-compliant version of fchmodat with flag argument 2012-01-13 1:53 [PATCH 0/2 RESEND] POSIX-compliant version of fchmodat with flag argument Andrew Ayer 2012-01-13 1:53 ` [PATCH 1/2] vfs: Add fchmodat4 syscall: " Andrew Ayer 2012-01-13 1:53 ` [PATCH 2/2] x86: Hook up new fchmodat4 syscall Andrew Ayer @ 2012-09-18 20:39 ` Kenny Root 2 siblings, 0 replies; 7+ messages in thread From: Kenny Root @ 2012-09-18 20:39 UTC (permalink / raw) To: Alexander Viro; +Cc: linux-fsdevel, linux-kernel, Andrew Ayer On Thu, Jan 12, 2012 at 05:53:44PM -0800, Andrew Ayer wrote: > Besides the POSIX-compliance, this patch will make it possible to > ensure, in a race-free way, that you do not follow symlinks when > chmodding. Previously, you could open a file with O_NOFOLLOW and fchmod > it, but this only worked if you had read or write permissions on the > file. Now you can open the file with O_PATH|O_NOFOLLOW and do fchmodat > with AT_EMPTY_PATH. Alexander, this patch solves a particular problem in a useful way. I find it useful and I would be happy to see it included in mainline. Thanks, Kenny ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2014-01-21 19:06 UTC | newest] Thread overview: 7+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2012-01-13 1:53 [PATCH 0/2 RESEND] POSIX-compliant version of fchmodat with flag argument Andrew Ayer 2012-01-13 1:53 ` [PATCH 1/2] vfs: Add fchmodat4 syscall: " Andrew Ayer 2014-01-21 7:30 ` Florian Weimer 2014-01-21 18:57 ` Andrew Ayer 2014-01-21 18:58 ` [PATCH] vfs: Add version of " Andrew Ayer 2012-01-13 1:53 ` [PATCH 2/2] x86: Hook up new fchmodat4 syscall Andrew Ayer 2012-09-18 20:39 ` [PATCH 0/2 RESEND] POSIX-compliant version of fchmodat with flag argument Kenny Root
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