| From ec564ec4f2654cdc6b48e5cd48fe7eb9d1eb6c93 Mon Sep 17 00:00:00 2001 |
| From: Andrey Ryabinin <aryabinin@virtuozzo.com> |
| Date: Thu, 25 Apr 2019 22:23:58 -0700 |
| Subject: mm/page_alloc.c: avoid potential NULL pointer dereference |
| |
| [ Upstream commit 8139ad043d632c0e9e12d760068a7a8e91659aa1 ] |
| |
| 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> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| mm/page_alloc.c | 3 +++ |
| 1 file changed, 3 insertions(+) |
| |
| diff --git a/mm/page_alloc.c b/mm/page_alloc.c |
| index eedb57f9b40b5..d59be95ba45cf 100644 |
| --- a/mm/page_alloc.c |
| +++ b/mm/page_alloc.c |
| @@ -3385,6 +3385,9 @@ 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; |
| |
| -- |
| 2.20.1 |
| |
