The POSIX.1 draft spec for utimensat() says that to do anything
other than setting both timestamps to a time other than the
current time (i.e., times is not NULL, and both tv_nsec fields
are not UTIME_NOW and both tv_nsec fields are not UTIME_OMIT),
either:
a) the caller's effective user ID must match the file owner; or
b) the caller must have appropriate privileges.
If this condition is violated, then the error EPERM should result.
However, the current implementation does not generate EPERM if
one tv_nsec field is UTIME_NOW while the other is UTIME_OMIT.
It should give this error for that case.
This patch:
a) Repairs that problem.
b) Removes the now unneeded nsec_special() helper function.
Miklos suggested an alternative idea, migrating the
is_owner_or_cap() checks into fs/attr.c:inode_change_ok() via
the use of an ATTR_OWNER_CHECK flag. Maybe we could do that
later, but for now I've gone with this version, which is
simpler, and can be more easily read as being correct.
CC: Miklos Szeredi <miklos@xxxxxxxxxx>
CC: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
CC: Ulrich Drepper <drepper@xxxxxxxxxx>
Signed-off-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
--- linux-2.6.26-rc4/fs/utimes.c 2008-06-03 23:11:53.000000000 +0200
+++ linux-2.6.26-rc4-utimensat-fix-v4/fs/utimes.c 2008-06-03 23:04:48.000000000 +0200
@@ -40,14 +40,9 @@
#endif
-static bool nsec_special(long nsec)
-{
- return nsec == UTIME_OMIT || nsec == UTIME_NOW;
-}
-
static bool nsec_valid(long nsec)
{
- if (nsec_special(nsec))
+ if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
return true;
return nsec >= 0 && nsec <= 999999999;
@@ -135,8 +130,7 @@
* 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))) {
+ if (!times) {
error = -EACCES;
if (IS_IMMUTABLE(inode))
goto mnt_drop_write_and_out;
@@ -151,6 +145,18 @@
goto mnt_drop_write_and_out;
}
}
+ } else if ((times[0].tv_nsec == UTIME_NOW &&
+ times[1].tv_nsec == UTIME_OMIT)
+ ||
+ (times[0].tv_nsec == UTIME_OMIT &&
+ times[1].tv_nsec == UTIME_NOW)) {
+ error =-EPERM;
+
+ if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
+ goto mnt_drop_write_and_out;
+
+ if (!is_owner_or_cap(inode))
+ goto mnt_drop_write_and_out;
}
mutex_lock(&inode->i_mutex);
error = notify_change(dentry, &newattrs);
--
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