linux-kernel - [ 038/184] mm: bugfix: set current->reclaim

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Message-Id: <20130604172131.885884951@1wt.eu>
Date:	Tue, 04 Jun 2013 19:22:08 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Takamori Yamaguchi <takamori.yamaguchi@...sony.com>,
	Aaditya Kumar <aaditya.kumar@...sony.com>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Willy Tarreau <w@....eu>
Subject: [ 038/184] mm: bugfix: set current->reclaim_state to NULL while

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------
 returning from kswapd()

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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Willy Tarreau <w@....eu>
---
 mm/vmscan.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4649929..738db2b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2241,6 +2241,8 @@ static int kswapd(void *p)
 			balance_pgdat(pgdat, order);
 		}
 	}
+
+	current->reclaim_state = NULL;
 	return 0;
 }
 
-- 
1.7.12.2.21.g234cd45.dirty



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