| From bippy-1.2.0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@kernel.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2025-37958: mm/huge_memory: fix dereferencing invalid pmd migration entry |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| mm/huge_memory: fix dereferencing invalid pmd migration entry |
| |
| When migrating a THP, concurrent access to the PMD migration entry during |
| a deferred split scan can lead to an invalid address access, as |
| illustrated below. To prevent this invalid access, it is necessary to |
| check the PMD migration entry and return early. In this context, there is |
| no need to use pmd_to_swp_entry and pfn_swap_entry_to_page to verify the |
| equality of the target folio. Since the PMD migration entry is locked, it |
| cannot be served as the target. |
| |
| Mailing list discussion and explanation from Hugh Dickins: "An anon_vma |
| lookup points to a location which may contain the folio of interest, but |
| might instead contain another folio: and weeding out those other folios is |
| precisely what the "folio != pmd_folio((*pmd)" check (and the "risk of |
| replacing the wrong folio" comment a few lines above it) is for." |
| |
| BUG: unable to handle page fault for address: ffffea60001db008 |
| CPU: 0 UID: 0 PID: 2199114 Comm: tee Not tainted 6.14.0+ #4 NONE |
| Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 |
| RIP: 0010:split_huge_pmd_locked+0x3b5/0x2b60 |
| Call Trace: |
| <TASK> |
| try_to_migrate_one+0x28c/0x3730 |
| rmap_walk_anon+0x4f6/0x770 |
| unmap_folio+0x196/0x1f0 |
| split_huge_page_to_list_to_order+0x9f6/0x1560 |
| deferred_split_scan+0xac5/0x12a0 |
| shrinker_debugfs_scan_write+0x376/0x470 |
| full_proxy_write+0x15c/0x220 |
| vfs_write+0x2fc/0xcb0 |
| ksys_write+0x146/0x250 |
| do_syscall_64+0x6a/0x120 |
| entry_SYSCALL_64_after_hwframe+0x76/0x7e |
| |
| The bug is found by syzkaller on an internal kernel, then confirmed on |
| upstream. |
| |
| The Linux kernel CVE team has assigned CVE-2025-37958 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 4.14 with commit 84c3fc4e9c563d8fb91cfdf5948da48fe1af34d3 and fixed in 6.12.29 with commit 6166c3cf405441f7147b322980144feb3cefc617 |
| Issue introduced in 4.14 with commit 84c3fc4e9c563d8fb91cfdf5948da48fe1af34d3 and fixed in 6.14.7 with commit fbab262b0c8226c697af1851a424896ed47dedcc |
| Issue introduced in 4.14 with commit 84c3fc4e9c563d8fb91cfdf5948da48fe1af34d3 and fixed in 6.15 with commit be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7 |
| |
| 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-2025-37958 |
| 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/huge_memory.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/6166c3cf405441f7147b322980144feb3cefc617 |
| https://git.kernel.org/stable/c/fbab262b0c8226c697af1851a424896ed47dedcc |
| https://git.kernel.org/stable/c/be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7 |
