Re: [PATCH] mm: fix null pointer dereference in wait_iff_congested()
From: Minchan Kim <minchan@kernel.org>
Date: 2012-12-28 02:49:33
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Hello Zlatko, On Fri, Dec 28, 2012 at 03:16:38AM +0100, Zlatko Calusic wrote:
From: Zlatko Calusic <redacted> 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?
quoted hunk ↗ jump to hunk
BUG: unable to handle kernel NULL pointer dereference IP: [<ffffffff811542d9>] wait_iff_congested+0x59/0x140 This trivial patch fixes it. Reported-by: Zhouping Liu <redacted> Reported-and-tested-by: Sedat Dilek <redacted> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Zlatko Calusic <redacted> --- 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 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>