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

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

From: Takamori Yamaguchi <[email protected]>

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 <[email protected]>
Signed-off-by: Aaditya Kumar <[email protected]>
Acked-by: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Ben Hutchings <[email protected]>
---
 mm/vmscan.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2624edc..8b055e9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3017,6 +3017,8 @@ static int kswapd(void *p)
                                                &balanced_classzone_idx);
                }
        }
+
+       current->reclaim_state = NULL;
        return 0;
 }
 


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