| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-49964: mm/hugetlb: fix memfd_pin_folios free_huge_pages leak |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| mm/hugetlb: fix memfd_pin_folios free_huge_pages leak |
| |
| memfd_pin_folios followed by unpin_folios fails to restore free_huge_pages |
| if the pages were not already faulted in, because the folio refcount for |
| pages created by memfd_alloc_folio never goes to 0. memfd_pin_folios |
| needs another folio_put to undo the folio_try_get below: |
| |
| memfd_alloc_folio() |
| alloc_hugetlb_folio_nodemask() |
| dequeue_hugetlb_folio_nodemask() |
| dequeue_hugetlb_folio_node_exact() |
| folio_ref_unfreeze(folio, 1); ; adds 1 refcount |
| folio_try_get() ; adds 1 refcount |
| hugetlb_add_to_page_cache() ; adds 512 refcount (on x86) |
| |
| With the fix, after memfd_pin_folios + unpin_folios, the refcount for the |
| (unfaulted) page is 512, which is correct, as the refcount for a faulted |
| unpinned page is 513. |
| |
| The Linux kernel CVE team has assigned CVE-2024-49964 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.11 with commit 89c1905d9c140372b7f50ef48f42378cf85d9bc5 and fixed in 6.11.3 with commit 59e081ff2e91bbf19b8c1ecb75b031f778858383 |
| Issue introduced in 6.11 with commit 89c1905d9c140372b7f50ef48f42378cf85d9bc5 and fixed in 6.12 with commit c56b6f3d801d7ec8965993342bdd9e2972b6cb8e |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-49964 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| mm/gup.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/59e081ff2e91bbf19b8c1ecb75b031f778858383 |
| https://git.kernel.org/stable/c/c56b6f3d801d7ec8965993342bdd9e2972b6cb8e |
