| 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-2024-35797: mm: cachestat: fix two shmem bugs |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| mm: cachestat: fix two shmem bugs |
| |
| When cachestat on shmem races with swapping and invalidation, there |
| are two possible bugs: |
| |
| 1) A swapin error can have resulted in a poisoned swap entry in the |
| shmem inode's xarray. Calling get_shadow_from_swap_cache() on it |
| will result in an out-of-bounds access to swapper_spaces[]. |
| |
| Validate the entry with non_swap_entry() before going further. |
| |
| 2) When we find a valid swap entry in the shmem's inode, the shadow |
| entry in the swapcache might not exist yet: swap IO is still in |
| progress and we're before __remove_mapping; swapin, invalidation, |
| or swapoff have removed the shadow from swapcache after we saw the |
| shmem swap entry. |
| |
| This will send a NULL to workingset_test_recent(). The latter |
| purely operates on pointer bits, so it won't crash - node 0, memcg |
| ID 0, eviction timestamp 0, etc. are all valid inputs - but it's a |
| bogus test. In theory that could result in a false "recently |
| evicted" count. |
| |
| Such a false positive wouldn't be the end of the world. But for |
| code clarity and (future) robustness, be explicit about this case. |
| |
| Bail on get_shadow_from_swap_cache() returning NULL. |
| |
| The Linux kernel CVE team has assigned CVE-2024-35797 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.5 with commit cf264e1329fb0307e044f7675849f9f38b44c11a and fixed in 6.6.24 with commit b79f9e1ff27c994a4c452235ba09e672ec698e23 |
| Issue introduced in 6.5 with commit cf264e1329fb0307e044f7675849f9f38b44c11a and fixed in 6.7.12 with commit d962f6c583458037dc7e529659b2b02b9dd3d94b |
| Issue introduced in 6.5 with commit cf264e1329fb0307e044f7675849f9f38b44c11a and fixed in 6.8.3 with commit 24a0e73d544439bb9329fbbafac44299e548a677 |
| Issue introduced in 6.5 with commit cf264e1329fb0307e044f7675849f9f38b44c11a and fixed in 6.9 with commit d5d39c707a4cf0bcc84680178677b97aa2cb2627 |
| |
| 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-2024-35797 |
| 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/filemap.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/b79f9e1ff27c994a4c452235ba09e672ec698e23 |
| https://git.kernel.org/stable/c/d962f6c583458037dc7e529659b2b02b9dd3d94b |
| https://git.kernel.org/stable/c/24a0e73d544439bb9329fbbafac44299e548a677 |
| https://git.kernel.org/stable/c/d5d39c707a4cf0bcc84680178677b97aa2cb2627 |
