From: David Carlier Date: Wed, 20 May 2026 04:49:12 +0000 (+0100) Subject: mm/hugetlb: restore reservation on error in hugetlb folio copy paths X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=40c81856e622a9dc59294a90d169ac07ea25b0b0;p=thirdparty%2Flinux.git mm/hugetlb: restore reservation on error in hugetlb folio copy paths Two sites in mm/hugetlb.c allocate a hugetlb folio via alloc_hugetlb_folio() (consuming a VMA reservation) and then call copy_user_large_folio(), which became int-returning in commit 1cb9dc4b475c ("mm: hwpoison: support recovery from HugePage copy-on-write faults") and can now fail (e.g. -EHWPOISON on a hwpoisoned source page). On the failure path, folio_put() restores the global hugetlb pool count through free_huge_folio(), but the per-VMA reservation map entry is left marked consumed: - hugetlb_mfill_atomic_pte() resubmission path (UFFDIO_COPY) - copy_hugetlb_page_range() fork-time CoW path when hugetlb_try_dup_anon_rmap() fails (rare: pinned hugetlb anon folio under fork) User-visible effect: on UFFDIO_COPY into a private hugetlb VMA where the resubmission copy fails, the reservation for that address is leaked from the VMA's reserve map. A subsequent fault at the same address takes the no-reservation path, and under hugetlb pool pressure the task is SIGBUSed at an address it had previously reserved. The fork-time CoW path leaks the same way in the child VMA's reserve map, though it requires the much rarer combination of pinned hugetlb anon page + hwpoisoned source. Add the missing restore_reserve_on_error() call before folio_put() on both error paths. Link: https://lore.kernel.org/20260520044912.6751-1-devnexen@gmail.com Fixes: 1cb9dc4b475c ("mm: hwpoison: support recovery from HugePage copy-on-write faults") Signed-off-by: David Carlier Reviewed-by: Muchun Song Cc: David Hildenbrand Cc: Mina Almasry Cc: Muchun Song Cc: Oscar Salvador Cc: yuehaibing Cc: Signed-off-by: Andrew Morton --- diff --git a/mm/hugetlb.c b/mm/hugetlb.c index ece86d9339ce..1b1d4f87a3a4 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4977,6 +4977,7 @@ again: addr, dst_vma); folio_put(pte_folio); if (ret) { + restore_reserve_on_error(h, dst_vma, addr, new_folio); folio_put(new_folio); break; } @@ -6273,6 +6274,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, folio_put(*foliop); *foliop = NULL; if (ret) { + restore_reserve_on_error(h, dst_vma, dst_addr, folio); folio_put(folio); goto out; }