| 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-2024-36943: fs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| fs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan |
| |
| make_uffd_wp_pte() was previously doing: |
| |
| pte = ptep_get(ptep); |
| ptep_modify_prot_start(ptep); |
| pte = pte_mkuffd_wp(pte); |
| ptep_modify_prot_commit(ptep, pte); |
| |
| But if another thread accessed or dirtied the pte between the first 2 |
| calls, this could lead to loss of that information. Since |
| ptep_modify_prot_start() gets and clears atomically, the following is the |
| correct pattern and prevents any possible race. Any access after the |
| first call would see an invalid pte and cause a fault: |
| |
| pte = ptep_modify_prot_start(ptep); |
| pte = pte_mkuffd_wp(pte); |
| ptep_modify_prot_commit(ptep, pte); |
| |
| The Linux kernel CVE team has assigned CVE-2024-36943 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.7 with commit 52526ca7fdb905a768a93f8faa418e9b988fc34b and fixed in 6.8.10 with commit 74b3d66f91d9f539f99faad74d796fa9a389a015 |
| Issue introduced in 6.7 with commit 52526ca7fdb905a768a93f8faa418e9b988fc34b and fixed in 6.9 with commit c70dce4982ce1718bf978a35f8e26160b82081f4 |
| |
| 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-2024-36943 |
| 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: |
| fs/proc/task_mmu.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/74b3d66f91d9f539f99faad74d796fa9a389a015 |
| https://git.kernel.org/stable/c/c70dce4982ce1718bf978a35f8e26160b82081f4 |
