Re: Q: check_unsafe_exec() races (Was: [PATCH 2/4] fix setuid sometimes doesn't)

Al Viro
2009-04-01T03:05:00Z

On Wed, Apr 01, 2009 at 03:38:49AM +0100, Al Viro wrote:
> On Wed, Apr 01, 2009 at 01:28:01AM +0100, Hugh Dickins wrote:
> > Minor bisectability issue: the third patch, which introduces
> > int unshare_fs_struct(void), needs to return 0 when it succeeds:
> > that gets corrected in the fourth patch.
>
> ACK.
>
> > Lockdep objects to how check_unsafe_exec nests write_lock(&p->fs_lock)
> > inside lock_task_sighand(p, &flags). It's right: we sometimes take
> > sighand->siglock in interrupt, so if such an interrupt occurred just
> > after you take fs_lock elsewhere, that could deadlock with this. It
> > seems happy with taking fs_lock just outside the lock_task_sighand.
>
> Right you are, check_unsafe_exec() reordered. Will push in a few.

Rebased and pushed (same tree, same branch; included into for-next, along
with related cleanups).