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 pObMw0hr 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Sat Oct 31, 2026 at 10:13 PM EDT, Gregory Price (Meta) wrote: > For a bind or preferred-many policy, mempolicy_slab_node() tests the > first matching slot's zone for NULL, then reads the slot again to look > up the zone's node. Offlining a zone's last block rebuilds the > zonelists in place, so the second read can return the terminator: > > CPU 0 CPU 1 > mempolicy_slab_node() > zonelist_zone(slot 4) > =3D node 2 NORMAL > offline_pages() > build_all_zonelists() > slot 4 =3D NULL > zonelist_node_idx(slot 4) > zone_to_nid(NULL) > > Current GCC merges the two reads, but nothing requires it. With > mm/mempolicy.o built with -fno-inline -fno-ipa-sra, holding a bound > task's slab_strict_numa allocation between the reads while a movable > block earlier in the zonelist goes offline oopses every time: > > BUG: kernel NULL pointer dereference, address: 0000000000000060 > RIP: 0010:zone_to_nid+0x0/0x10 > Call Trace: > kmem_cache_alloc_noprof+0x294/0x610 > do_getname+0x34/0x230 > > mempolicy_slab_node() and zonelist_node_idx() are tail calls here, so > neither appears in the trace. > > Read the slot once and use that zone. > > Fixes: 11cd8638c37f ("mm, page_alloc: remove stop_machine from build_all_= zonelists") > Cc: stable@vger.kernel.org > Signed-off-by: Gregory Price (Meta) > Reviewed-by: Vlastimil Babka (SUSE) > --- > mm/mempolicy.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > Reviewed-by: Zi Yan --=20 Best Regards, Yan, Zi