Messages in this thread Patch in this message | | | Date | Sat, 03 May 2008 14:27:54 +0200 | From | Oliver Pinter <> | Subject | [OP] 04-vfs-fix-permission-checking-in-sys_utimensat.patch added to queue-2.6.22.23-op1 |
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Your patch added to queue-2.6.22.23-op1. If anyone has any objections, please let us know.
http://repo.or.cz/w/linux-2.6.22.y-op-patches.git git://repo.or.cz/linux-2.6.22.y-op-patches.git
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From: Miklos Szeredi <mszeredi@suse.cz> Date: Thu, 1 May 2008 04:34:45 -0700 Subject: [PATCH] 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> Backported-to-2.6.22.y: Oliver Pinter <oliver.pntr@gmail.com>
diff --git a/fs/utimes.c b/fs/utimes.c index f28a919..88432eb 100644 --- a/fs/utimes.c +++ b/fs/utimes.c @@ -39,9 +39,14 @@ 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; @@ -115,7 +120,15 @@ 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 dput_and_out;
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