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authorAndrey Ryabinin <aryabinin@virtuozzo.com>2019-04-25 22:23:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-04-26 09:18:05 -0700
commit8139ad043d632c0e9e12d760068a7a8e91659aa1 (patch)
tree0f1168febb3f2741513726bd7832a419147cde35
parentee8ab0eeb49bd3982090c8f14dc9cc65bcd13c5c (diff)
download96b-common-8139ad043d632c0e9e12d760068a7a8e91659aa1.tar.gz
mm/page_alloc.c: avoid potential NULL pointer dereference
ac.preferred_zoneref->zone passed to alloc_flags_nofragment() can be NULL. 'zone' pointer unconditionally derefernced in alloc_flags_nofragment(). Bail out on NULL zone to avoid potential crash. Currently we don't see any crashes only because alloc_flags_nofragment() has another bug which allows compiler to optimize away all accesses to 'zone'. Link: http://lkml.kernel.org/r/20190423120806.3503-1-aryabinin@virtuozzo.com Fixes: 6bb154504f8b ("mm, page_alloc: spread allocations across zones before introducing fragmentation") Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Acked-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_alloc.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d167c48d913c..9992ca7f29f1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3432,6 +3432,9 @@ alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask)
alloc_flags |= ALLOC_KSWAPD;
#ifdef CONFIG_ZONE_DMA32
+ if (!zone)
+ return alloc_flags;
+
if (zone_idx(zone) != ZONE_NORMAL)
goto out;