Re: [PATCH] mm: pass mm to grab_swap_token
From: Minchan Kim
Date: Sun Jun 21 2009 - 20:40:20 EST
On Sun, 21 Jun 2009 14:02:43 +0100 (BST)
Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx> 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@xxxxxxxxxx>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Signed-off-by: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
> Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
I already added my sign to Hannes but it is folded in this patch.
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