mainline inclusion from mainline-v6.16 commit 9f1e8cd0b7c4c944e9921b52a6661b5eda2705ab category: bugfix bugzilla: CVE-2025-37834 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- In shrink_folio_list(), the hwpoisoned folio may be large folio, which can't be handled by unmap_poisoned_folio(). For THP, try_to_unmap_one() must be passed with TTU_SPLIT_HUGE_PMD to split huge PMD first and then retry. Without TTU_SPLIT_HUGE_PMD, we will trigger null-ptr deref of pvmw.pte. Even we passed TTU_SPLIT_HUGE_PMD, we will trigger a WARN_ON_ONCE due to the page isn't in swapcache. Since UCE is rare in real world, and race with reclaimation is more rare, just skipping the hwpoisoned large folio is enough. memory_failure() will handle it if the UCE is triggered again. This happens when memory reclaim for large folio races with memory_failure(), and will lead to kernel panic. The race is as follows: cpu0 cpu1 shrink_folio_list memory_failure TestSetPageHWPoison unmap_poisoned_folio --> trigger BUG_ON due to unmap_poisoned_folio couldn't handle large folio [tujinjiang@huawei.com: add comment to unmap_poisoned_folio()] Link: https://lkml.kernel.org/r/69fd4e00-1b13-d5f7-1c82-705c7d977ea4@huawei.com Link: https://lkml.kernel.org/r/20250627125747.3094074-2-tujinjiang@huawei.com Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com> Fixes: 1b0449544c64 ("mm/vmscan: don't try to reclaim hwpoison folio") Reported-by: syzbot+3b220254df55d8ca8a61@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68412d57.050a0220.2461cf.000e.GAE@google.com/ Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> Acked-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Conflicts: mm/vmscan.c mm/memory-failure.c [Conflicts due to folio isn't introduced.] Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com> --- mm/vmscan.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 1374d46a1b5c..e82d7995b548 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1328,6 +1328,9 @@ static unsigned int shrink_page_list(struct list_head *page_list, goto keep; if (PageHWPoison(page)) { + if (PageTransHuge(page)) + goto keep_locked; + try_to_unmap(page, TTU_IGNORE_MLOCK); unlock_page(page); put_page(page); -- 2.43.0