| 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-2025-21709: kernel: be more careful about dup_mmap() failures and uprobe registering |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| kernel: be more careful about dup_mmap() failures and uprobe registering |
| |
| If a memory allocation fails during dup_mmap(), the maple tree can be left |
| in an unsafe state for other iterators besides the exit path. All the |
| locks are dropped before the exit_mmap() call (in mm/mmap.c), but the |
| incomplete mm_struct can be reached through (at least) the rmap finding |
| the vmas which have a pointer back to the mm_struct. |
| |
| Up to this point, there have been no issues with being able to find an |
| mm_struct that was only partially initialised. Syzbot was able to make |
| the incomplete mm_struct fail with recent forking changes, so it has been |
| proven unsafe to use the mm_struct that hasn't been initialised, as |
| referenced in the link below. |
| |
| Although 8ac662f5da19f ("fork: avoid inappropriate uprobe access to |
| invalid mm") fixed the uprobe access, it does not completely remove the |
| race. |
| |
| This patch sets the MMF_OOM_SKIP to avoid the iteration of the vmas on the |
| oom side (even though this is extremely unlikely to be selected as an oom |
| victim in the race window), and sets MMF_UNSTABLE to avoid other potential |
| users from using a partially initialised mm_struct. |
| |
| When registering vmas for uprobe, skip the vmas in an mm that is marked |
| unstable. Modifying a vma in an unstable mm may cause issues if the mm |
| isn't fully initialised. |
| |
| The Linux kernel CVE team has assigned CVE-2025-21709 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.8 with commit d2406291483775ecddaee929231a39c70c08fda2 and fixed in 6.13.2 with commit da139948aeda677ac09cc0e7d837f8a314de7d55 |
| Issue introduced in 6.8 with commit d2406291483775ecddaee929231a39c70c08fda2 and fixed in 6.14 with commit 64c37e134b120fb462fb4a80694bfb8e7be77b14 |
| |
| 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-2025-21709 |
| 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: |
| kernel/events/uprobes.c |
| kernel/fork.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/da139948aeda677ac09cc0e7d837f8a314de7d55 |
| https://git.kernel.org/stable/c/64c37e134b120fb462fb4a80694bfb8e7be77b14 |
