[merged mm-stable] mm-hugetlb-fix-use-after-free-in-hugetlb_mfill_atomic_pte.patch removed from -mm tree

[merged mm-stable] mm-hugetlb-fix-use-after-free-in-hugetlb_mfill_atomic_pte.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/hugetlb: fix use-after-free in hugetlb_mfill_atomic_pte()
has been removed from the -mm tree.  Its filename was
     mm-hugetlb-fix-use-after-free-in-hugetlb_mfill_atomic_pte.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: "David Hildenbrand (Arm)" <david@kernel.org>
Subject: mm/hugetlb: fix use-after-free in hugetlb_mfill_atomic_pte()
Date: Thu, 15 Oct 2026 18:07:09 +0200

Let's fix another instance where we use a folio after dropping the PTL,
where someone else could e.g., MADV_DONTNEED it once we drop the PTL,
making us trigger a use-after-free on the folio.

Link: https://lore.kernel.org/20261015-urgent_fixes-v1-3-42796911043b@kernel.org
Fixes: cb6acd01e2e4 ("hugetlbfs: fix races and page leaks during migration")
Fixes: 1c9e8def43a3 ("userfaultfd: hugetlbfs: add UFFDIO_COPY support for shared mappings")
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Acked-by: Muchun Song <muchun.song@linux.dev>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Adam Litke <agl@us.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Rik van Riel <riel@surriel.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Kiryl Shutsemau <kas@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: <stable@vger.kernel.org>
---

 mm/hugetlb.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/mm/hugetlb.c~mm-hugetlb-fix-use-after-free-in-hugetlb_mfill_atomic_pte
+++ a/mm/hugetlb.c
@@ -6520,11 +6520,16 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_
 	/* No need to invalidate - it was non-present before */
 	update_mmu_cache(dst_vma, dst_addr, dst_pte);
 
-	spin_unlock(ptl);
 	if (!is_continue)
 		folio_set_hugetlb_migratable(folio);
 	if (vm_shared || is_continue)
 		folio_unlock(folio);
+
+	/*
+	 * Hold the PTL until we're done with the folio: the page table owns the
+	 * folio reference now.
+	 */
+	spin_unlock(ptl);
 	ret = 0;
 out:
 	return ret;
_

Patches currently in -mm which might be from david@kernel.org are

mm-fix-address-wraparound-when-scanning-large-folio-ptes.patch
mm-hugetlb-disable-pmd-sharing-for-uffd-missing-mode.patch
mm-vma-write-lock-source-vma-before-duplicating-it-in-__split_vma.patch
mm-madvise-preserve-vma_softdirty_bit-when-changing-anonymous-names.patch