Doug / smarc-fsl-linux-kernel

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Commit 02c6be615f1fcd37ac5ed93a3ad6692ad8991cd9

Authored by Miklos Szeredi
Committed by Linus Torvalds
1 parent 2850699c59
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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>

Showing 1 changed file with 15 additions and 2 deletions Side-by-side Diff

... ... @@ -40,9 +40,14 @@
40 40  
41 41 #endif
42 42  
  43 +static bool nsec_special(long nsec)
  44 +{
  45 + return nsec == UTIME_OMIT || nsec == UTIME_NOW;
  46 +}
  47 +
43 48 static bool nsec_valid(long nsec)
44 49 {
45   - if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
  50 + if (nsec_special(nsec))
46 51 return true;
47 52  
48 53 return nsec >= 0 && nsec <= 999999999;
... ... @@ -119,7 +124,15 @@
119 124 newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
120 125 newattrs.ia_valid |= ATTR_MTIME_SET;
121 126 }
122   - } else {
  127 + }
  128 +
  129 + /*
  130 + * If times is NULL or both times are either UTIME_OMIT or
  131 + * UTIME_NOW, then need to check permissions, because
  132 + * inode_change_ok() won't do it.
  133 + */
  134 + if (!times || (nsec_special(times[0].tv_nsec) &&
  135 + nsec_special(times[1].tv_nsec))) {
123 136 error = -EACCES;
124 137 if (IS_IMMUTABLE(inode))
125 138 goto mnt_drop_write_and_out;