Re: [PATCH] mm: pass mm to grab_swap_token

Minchan Kim
2009-06-22T00:40:11Z

On Sun, 21 Jun 2009 14:02:43 +0100 (BST)
Hugh Dickins <hugh.dickins@tiscali.co.uk> wrote:

> If a kthread happens to use get_user_pages() on an mm (as KSM does),
> there's a chance that it will end up trying to read in a swap page,
> then oops in grab_swap_token() because the kthread has no mm: GUP
> passes down the right mm, so grab_swap_token() ought to be using it.
>
> We have not identified a stronger case than KSM's daemon (not yet
> in mainline), but the issue must have come up before, since RHEL has
> included a fix for this for years (though a different fix, they just
> back out of grab_swap_token if current->mm is unset: which is what
> we first proposed, but using the right mm here seems more correct).
>
> Reported-by: Izik Eidus <ieidus@redhat.com>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
> Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>

I already added my sign to Hannes but it is folded in this patch.

--
Kinds Regards
Minchan Kim