The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 7810e6781e0fcbca78b91cf65053f895bf59e85f Mon Sep 17 00:00:00 2001
From: Vlastimil Babka vbabka@suse.cz Date: Thu, 7 Jun 2018 17:09:29 -0700 Subject: [PATCH] mm, page_alloc: do not break __GFP_THISNODE by zonelist reset
In __alloc_pages_slowpath() we reset zonelist and preferred_zoneref for allocations that can ignore memory policies. The zonelist is obtained from current CPU's node. This is a problem for __GFP_THISNODE allocations that want to allocate on a different node, e.g. because the allocating thread has been migrated to a different CPU.
This has been observed to break SLAB in our 4.4-based kernel, because there it relies on __GFP_THISNODE working as intended. If a slab page is put on wrong node's list, then further list manipulations may corrupt the list because page_to_nid() is used to determine which node's list_lock should be locked and thus we may take a wrong lock and race.
Current SLAB implementation seems to be immune by luck thanks to commit 511e3a058812 ("mm/slab: make cache_grow() handle the page allocated on arbitrary node") but there may be others assuming that __GFP_THISNODE works as promised.
We can fix it by simply removing the zonelist reset completely. There is actually no reason to reset it, because memory policies and cpusets don't affect the zonelist choice in the first place. This was different when commit 183f6371aac2 ("mm: ignore mempolicies when using ALLOC_NO_WATERMARK") introduced the code, as mempolicies provided their own restricted zonelists.
We might consider this for 4.17 although I don't know if there's anything currently broken.
SLAB is currently not affected, but in kernels older than 4.7 that don't yet have 511e3a058812 ("mm/slab: make cache_grow() handle the page allocated on arbitrary node") it is. That's at least 4.4 LTS. Older ones I'll have to check.
So stable backports should be more important, but will have to be reviewed carefully, as the code went through many changes. BTW I think that also the ac->preferred_zoneref reset is currently useless if we don't also reset ac->nodemask from a mempolicy to NULL first (which we probably should for the OOM victims etc?), but I would leave that for a separate patch.
Link: http://lkml.kernel.org/r/20180525130853.13915-1-vbabka@suse.cz Signed-off-by: Vlastimil Babka vbabka@suse.cz Fixes: 183f6371aac2 ("mm: ignore mempolicies when using ALLOC_NO_WATERMARK") Acked-by: Mel Gorman mgorman@techsingularity.net Cc: Michal Hocko mhocko@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Vlastimil Babka vbabka@suse.cz Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ef1811531999..07b3c23762ad 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4169,7 +4169,6 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, * orientated. */ if (!(alloc_flags & ALLOC_CPUSET) || reserve_flags) { - ac->zonelist = node_zonelist(numa_node_id(), gfp_mask); ac->preferred_zoneref = first_zones_zonelist(ac->zonelist, ac->high_zoneidx, ac->nodemask); }