From 8ce41b0f9d77cca074df25afd39b86e2ee3aa68e Mon Sep 17 00:00:00 2001 From: Jinjiang Tu Date: Wed, 13 Nov 2024 16:32:35 +0800 Subject: [PATCH] mm: fix NULL pointer dereference in alloc_pages_bulk_noprof We triggered a NULL pointer dereference for ac.preferred_zoneref->zone in alloc_pages_bulk_noprof() when the task is migrated between cpusets. When cpuset is enabled, in prepare_alloc_pages(), ac->nodemask may be ¤t->mems_allowed. when first_zones_zonelist() is called to find preferred_zoneref, the ac->nodemask may be modified concurrently if the task is migrated between different cpusets. Assuming we have 2 NUMA Node, when traversing Node1 in ac->zonelist, the nodemask is 2, and when traversing Node2 in ac->zonelist, the nodemask is 1. As a result, the ac->preferred_zoneref points to NULL zone. In alloc_pages_bulk_noprof(), for_each_zone_zonelist_nodemask() finds a allowable zone and calls zonelist_node_idx(ac.preferred_zoneref), leading to NULL pointer dereference. __alloc_pages_noprof() fixes this issue by checking NULL pointer in commit ea57485af8f4 ("mm, page_alloc: fix check for NULL preferred_zone") and commit df76cee6bbeb ("mm, page_alloc: remove redundant checks from alloc fastpath"). To fix it, check NULL pointer for preferred_zoneref->zone. Link: https://lkml.kernel.org/r/20241113083235.166798-1-tujinjiang@huawei.com Fixes: 387ba26fb1cb ("mm/page_alloc: add a bulk page allocator") Signed-off-by: Jinjiang Tu Reviewed-by: Vlastimil Babka Cc: Alexander Lobakin Cc: David Hildenbrand Cc: Kefeng Wang Cc: Mel Gorman Cc: Nanyong Sun Cc: Signed-off-by: Andrew Morton --- mm/page_alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 216fbbfbedcf..b6958333054d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4607,7 +4607,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid, gfp = alloc_gfp; /* Find an allowed local zone that meets the low watermark. */ - for_each_zone_zonelist_nodemask(zone, z, ac.zonelist, ac.highest_zoneidx, ac.nodemask) { + z = ac.preferred_zoneref; + for_next_zone_zonelist_nodemask(zone, z, ac.highest_zoneidx, ac.nodemask) { unsigned long mark; if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) &&