mm: bugfix: set current->reclaim_state to NULL while returning from kswapd()

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2624edcfb42095d6e91ae79c7ca30e0e4838a0fd..8b055e9379bc23105dea4e58d6bebe2600756a4b 100644 (file)
--- 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;
 }