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U2FsdGVkX18PYW3Uf55ItGmu9lPMFsCfVLl8t3koMf9/JwKnoIu9DEF3QhZAAUCFg2QyEhAgVfFWTqk9jRG+8XOn46L9FWhrGgETpavYabpoHN7wPckeixRO2XbuIxa+zkBSzNRNTmm4Pjc9noRrHRSE0P2S+UY1fkcNBXBaj/tbXJQQfV/cL1VzU3J4dwajgCr2b+cXWrPuNWadcLDM8B8Qm7Tof1WEpZ7SzHmHIcDs51jgUZr6c5rHfCnBZOzhPZ9VxB2wxGRpQWOuPnMip9IaJdKfR0Lxqqh2gdCVsBvtz2d/rBx4ruUW0yI/TQBtV0QnVAYedhuucc+ckGUKKSEZgKGHd6IHJLcDhDV+Y0HC9J0uRjxJkftmqSFnBJ8BTDWkGWwU7D4ShUJTXN9yvZXtXe3wWPQtMrjDiUcWqLNIcxLl7K9CwAiUCdiwjkwAdqDi1+LPMOY5Okxl0B3ZkSo2iqKg697tJz7J7n1iPSErIXvW9/DbWmem/bDAO0FCthHZ1iNJwN/FP6HrROrcM/8154248bmLJCGxsx1rKmAWmTba5DmMYLDIt9MMiTXXjHybgFCvLeFLIP3/QcY5oQ/Qb9pwxfCl1ReQIkKyYvKjkyisdCjXTBi/4DXQ0Ag7Du9hbc+kgy+CRi2yN1AOwDJoWVxmDNhvemVAsK54KswtOACOy9ZsG7AXFpYC0sjkgSPQUde9g8jFgo34JqT3OND82aA2742bMqv7RmENJaAjTsUpch8+o9gRuDjvtmzif5jxI72XVg6dvwz4JUFI5GBYNC4DbT2kv6eZtFpYGBtxukUUCO2PjlJKDTminscHZ7fi886c7sMKOnSpp+YmElJmPX6gbaD0Ie2RYFA9nB/6deiXYwAC+1FUsNj0Sw93zQn956V/b4LH43Ydq4iDsk8PX4W/cuuFKdXgRfiOvIMXEyZFFgTiwwGWHvEgUIzRG6cTvXPF0JYEjZeOt/7 3wu1PNUo 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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: > __next_zones_zonelist() tests a 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 > __next_zones_zonelist(nodemask) > zonelist_zone(slot 1) =3D NORMAL > offline_pages() > build_all_zonelists() > [MOVABLE, NORMAL, NULL] > -> [NORMAL, NULL] > zref_in_nodemask(slot 1) > zone_to_nid(NULL) > > Current GCC and clang merge the two reads, but nothing requires it. > With mm/mmzone.o built with -fno-inline -fno-ipa-sra, holding a > nodemask allocation between the reads while the node's last movable > block goes offline oopses every time: > > BUG: kernel NULL pointer dereference, address: 0000000000000060 > RIP: 0010:zone_to_nid+0x0/0x10 > Call Trace: > zref_in_nodemask+0x9/0x20 > __next_zones_zonelist+0x23/0x70 > prepare_alloc_pages.constprop.0+0x16c/0x190 > __alloc_frozen_pages_noprof+0xaf/0x330 > > Read the slot once and test that zone. A NULL zone still ends the walk. It is better to spell out the rename from zref_in_nodemask() to zone_in_nodemask(). > > 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/mmzone.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > Makes sense. Reviewed-by: Zi Yan --=20 Best Regards, Yan, Zi