| Message ID | 20190423120806.3503-1-aryabinin@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] mm/page_alloc: avoid potential NULL pointer dereference | expand |
On Tue, Apr 23, 2019 at 03:08:05PM +0300, Andrey Ryabinin wrote: > 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'. > > 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>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 933bd42899e8..2b2c7065102f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3461,6 +3461,9 @@ 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;
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'. Fixes: 6bb154504f8b ("mm, page_alloc: spread allocations across zones before introducing fragmentation") Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+)