CVE-2026-53154

In the Linux kernel, the following vulnerability has been resolved:

mm/hugetlb: restore reservation on error in hugetlb folio copy paths

Two sites in mm/hugetlb.c allocate a hugetlb folio via allochugetlbfolio() (consuming a VMA reservation) and then call copyuserlargefolio(), 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, folioput() restores the global hugetlb pool count through freehugefolio(), but the per-VMA reservation map entry is left marked consumed:

• hugetlbmfillatomicpte() resubmission path (UFFDIOCOPY)
• copyhugetlbpagerange() fork-time CoW path when hugetlbtrydupanon_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 restorereserveonerror() call before folioput() on both error paths.