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

    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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