From: Minchan Kim <minchan@kernel.org>
To: Zlatko Calusic <zlatko.calusic@iskon.hr>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Hugh Dickins <hughd@google.com>, linux-mm <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Zhouping Liu <zliu@redhat.com>,
Sedat Dilek <sedat.dilek@gmail.com>
Subject: Re: [PATCH] mm: fix null pointer dereference in wait_iff_congested()
Date: Fri, 28 Dec 2012 11:49:28 +0900 [thread overview]
Message-ID: <20121228024928.GA19720@blaptop> (raw)
In-Reply-To: <50DD0106.7040001@iskon.hr>
Hello Zlatko,
On Fri, Dec 28, 2012 at 03:16:38AM +0100, Zlatko Calusic wrote:
> From: Zlatko Calusic <zlatko.calusic@iskon.hr>
>
> The unintended consequence of commit 4ae0a48b is that
> wait_iff_congested() can now be called with NULL struct zone*
> producing kernel oops like this:
For good description, it would be better to write simple pseudo code
flow to show how NULL-zone pass into wait_iff_congested because
kswapd code flow is too complex.
As I see the code, we have following line above wait_iff_congested.
if (!unbalanced_zone || blah blah)
break;
How can NULL unbalanced_zone reach wait_iff_congested?
>
> BUG: unable to handle kernel NULL pointer dereference
> IP: [<ffffffff811542d9>] wait_iff_congested+0x59/0x140
>
> This trivial patch fixes it.
>
> Reported-by: Zhouping Liu <zliu@redhat.com>
> Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Hugh Dickins <hughd@google.com>
> Signed-off-by: Zlatko Calusic <zlatko.calusic@iskon.hr>
> ---
> mm/vmscan.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 02bcfa3..e55ce55 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2782,7 +2782,7 @@ loop_again:
> if (total_scanned && (sc.priority < DEF_PRIORITY - 2)) {
> if (has_under_min_watermark_zone)
> count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
> - else
> + else if (unbalanced_zone)
> wait_iff_congested(unbalanced_zone, BLK_RW_ASYNC, HZ/10);
> }
>
> --
> 1.8.1.rc3
>
> --
> Zlatko
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
--
Kind regards,
Minchan Kim
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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next prev parent reply other threads:[~2012-12-28 2:49 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-19 23:17 [PATCH] mm: do not sleep in balance_pgdat if there's no i/o congestion Zlatko Calusic
2012-12-19 23:25 ` Zlatko Calusic
2012-12-21 11:51 ` Hillf Danton
2012-12-27 15:42 ` Zlatko Calusic
2012-12-29 7:25 ` Hillf Danton
2012-12-29 12:11 ` Zlatko Calusic
2012-12-20 11:12 ` Mel Gorman
2012-12-20 20:58 ` Andrew Morton
2012-12-22 18:54 ` [PATCH] mm: modify pgdat_balanced() so that it also handles order=0 Zlatko Calusic
2012-12-23 14:12 ` [PATCH v2] " Zlatko Calusic
2012-12-26 15:07 ` [PATCH] mm: avoid calling pgdat_balanced() needlessly Zlatko Calusic
2012-12-28 2:16 ` [PATCH] mm: fix null pointer dereference in wait_iff_congested() Zlatko Calusic
2012-12-28 2:49 ` Minchan Kim [this message]
2012-12-28 13:29 ` Zlatko Calusic
2012-12-31 0:50 ` Minchan Kim
2012-12-29 8:45 ` Sedat Dilek
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