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author | Miklos Szeredi <mszeredi@suse.cz> | 2008-05-01 04:34:45 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-05-01 08:03:59 -0700 |
commit | 02c6be615f1fcd37ac5ed93a3ad6692ad8991cd9 (patch) | |
tree | 9c5047ed8b165a3388d5c61b2702f7cc12954766 /fs | |
parent | 2850699c59d513a0cd0c68f60f75609a5f9d4d32 (diff) | |
download | linux-3.10-02c6be615f1fcd37ac5ed93a3ad6692ad8991cd9.tar.gz linux-3.10-02c6be615f1fcd37ac5ed93a3ad6692ad8991cd9.tar.bz2 linux-3.10-02c6be615f1fcd37ac5ed93a3ad6692ad8991cd9.zip |
vfs: fix permission checking in sys_utimensat
If utimensat() is called with both times set to UTIME_NOW or one of them to
UTIME_NOW and the other to UTIME_OMIT, then it will update the file time
without any permission checking.
I don't think this can be used for anything other than a local DoS, but could
be quite bewildering at that (e.g. "Why was that large source tree rebuilt
when I didn't modify anything???")
This affects all kernels from 2.6.22, when the utimensat() syscall was
introduced.
Fix by doing the same permission checking as for the "times == NULL" case.
Thanks to Michael Kerrisk, whose utimensat-non-conformances-and-fixes.patch in
-mm also fixes this (and breaks other stuff), only he didn't realize the
security implications of this bug.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/utimes.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/fs/utimes.c b/fs/utimes.c index a2bef77dc9c..af059d5cb48 100644 --- a/fs/utimes.c +++ b/fs/utimes.c @@ -40,9 +40,14 @@ asmlinkage long sys_utime(char __user *filename, struct utimbuf __user *times) #endif +static bool nsec_special(long nsec) +{ + return nsec == UTIME_OMIT || nsec == UTIME_NOW; +} + static bool nsec_valid(long nsec) { - if (nsec == UTIME_OMIT || nsec == UTIME_NOW) + if (nsec_special(nsec)) return true; return nsec >= 0 && nsec <= 999999999; @@ -119,7 +124,15 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags newattrs.ia_mtime.tv_nsec = times[1].tv_nsec; newattrs.ia_valid |= ATTR_MTIME_SET; } - } else { + } + + /* + * If times is NULL or both times are either UTIME_OMIT or + * UTIME_NOW, then need to check permissions, because + * inode_change_ok() won't do it. + */ + if (!times || (nsec_special(times[0].tv_nsec) && + nsec_special(times[1].tv_nsec))) { error = -EACCES; if (IS_IMMUTABLE(inode)) goto mnt_drop_write_and_out; |