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SubjectRe: 2.6.22-rc6(mm1) Unable to handle kernel NULL pointer dereference - git-bisect result
On Sun, Jul 08, 2007 at 11:24:53AM -0700, Ulrich Drepper wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Linus Torvalds wrote:
> > notify_change() does *not* do permission checks for
> > ATTR_CTIME/MTIME/ATIME.
>
> Then I don't understand
>
> /* Check for setting the inode time. */
> if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
> if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
> goto error;
> }
>
> in inode_change_ok. This seems to me exactly like the check needed.

Sigh... There are two operations.
1) set the timestamp to user-supplied value. Owner-only.
2) have the timestamp set to _now_. Obviously can be done not
only by the owner (think of e.g. write(2)); having write access is
sufficient.

ATTR_MTIME_SET is the former. ATTR_MTIME without ATTR_MTIME_SET is the
latter and that's what utimes(foo, NULL) ends up doing.
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