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

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Date:	Thu, 13 Dec 2012 11:57:14 -0200
From:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Takamori Yamaguchi <takamori.yamaguchi@...sony.com>,
	Aaditya Kumar <aaditya.kumar@...sony.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
Subject: [PATCH 069/241] mm: bugfix: set current->reclaim_state to NULL while returning from kswapd()

3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

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

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

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;
 }
 
-- 
1.7.9.5

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