CVE-2026-53154— mm/hugetlb: restore reservation on error in hugetlb folio copy paths

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

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 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.

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Linux kernel 安全漏洞

Linux kernel是美国Linux基金会开源的操作系统Linux所使用的内核。 Linux kernel 6.4版本存在安全漏洞，该漏洞源于mm/hugetlb.c中的hugetlb folio复制路径在错误时未恢复预留，可能导致通过UFFDIO_COPY或fork时CoW路径泄露VMA预留映射中的预留，后续同一地址的缺页错误可能因hugetlb池压力导致任务收到SIGBUS信号。

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