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[069/241] mm: bugfix: set current->reclaim_state to NULL while returning from kswapd()

Message ID 1355407206-17100-70-git-send-email-herton.krzesinski@canonical.com
State New
Headers show

Commit Message

Herton Ronaldo Krzesinski Dec. 13, 2012, 1:57 p.m. UTC 
3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takamori Yamaguchi <takamori.yamaguchi@jp.sony.com>

commit b0a8cc58e6b9aaae3045752059e5e6260c0b94bc upstream.

In kswapd(), set current->reclaim_state to NULL before returning, as
current->reclaim_state holds reference to variable on kswapd()'s stack.

In rare cases, while returning from kswapd() during memory offlining,
__free_slab() and freepages() can access the dangling pointer of
current->reclaim_state.

Signed-off-by: Takamori Yamaguchi <takamori.yamaguchi@jp.sony.com>
Signed-off-by: Aaditya Kumar <aaditya.kumar@ap.sony.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
 mm/vmscan.c |    2 ++
 1 file changed, 2 insertions(+)
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Patch

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f0f8ebb..cdfdfc5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2835,6 +2835,8 @@  static int kswapd(void *p)
 						&balanced_classzone_idx);
 		}
 	}
+
+	current->reclaim_state = NULL;
 	return 0;
 }