numa: fix slab_node(MPOL_BIND)

When a node contains only HighMem memory, slab_node(MPOL_BIND)
dereferences a NULL pointer.

[ This code seems to go back all the way to commit 19770b32609b: "mm:
  filter based on a nodemask as well as a gfp_mask".  Which was back in
  April 2008, and it got merged into 2.6.26.  - Linus ]

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <cl@linux.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 81a127643aea..4a57f135b76e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1597,7 +1597,7 @@ unsigned slab_node(struct mempolicy *policy)
                 (void)first_zones_zonelist(zonelist, highest_zoneidx,
                                                         &policy->v.nodes,
                                                         &zone);
-                return zone->node;
+                return zone ? zone->node : numa_node_id();
         }
 
         default: