6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jinjiang Tu tujinjiang@huawei.com
commit 8ce41b0f9d77cca074df25afd39b86e2ee3aa68e upstream.
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 tujinjiang@huawei.com Reviewed-by: Vlastimil Babka vbabka@suse.cz Cc: Alexander Lobakin alobakin@pm.me Cc: David Hildenbrand david@redhat.com Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: Mel Gorman mgorman@techsingularity.net Cc: Nanyong Sun sunnanyong@huawei.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/page_alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4301,7 +4301,8 @@ unsigned long __alloc_pages_bulk(gfp_t g 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) &&