| 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-2025-37747: perf: Fix hang while freeing sigtrap event |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| perf: Fix hang while freeing sigtrap event |
| |
| Perf can hang while freeing a sigtrap event if a related deferred |
| signal hadn't managed to be sent before the file got closed: |
| |
| perf_event_overflow() |
| task_work_add(perf_pending_task) |
| |
| fput() |
| task_work_add(____fput()) |
| |
| task_work_run() |
| ____fput() |
| perf_release() |
| perf_event_release_kernel() |
| _free_event() |
| perf_pending_task_sync() |
| task_work_cancel() -> FAILED |
| rcuwait_wait_event() |
| |
| Once task_work_run() is running, the list of pending callbacks is |
| removed from the task_struct and from this point on task_work_cancel() |
| can't remove any pending and not yet started work items, hence the |
| task_work_cancel() failure and the hang on rcuwait_wait_event(). |
| |
| Task work could be changed to remove one work at a time, so a work |
| running on the current task can always cancel a pending one, however |
| the wait / wake design is still subject to inverted dependencies when |
| remote targets are involved, as pictured by Oleg: |
| |
| T1 T2 |
| |
| fd = perf_event_open(pid => T2->pid); fd = perf_event_open(pid => T1->pid); |
| close(fd) close(fd) |
| <IRQ> <IRQ> |
| perf_event_overflow() perf_event_overflow() |
| task_work_add(perf_pending_task) task_work_add(perf_pending_task) |
| </IRQ> </IRQ> |
| fput() fput() |
| task_work_add(____fput()) task_work_add(____fput()) |
| |
| task_work_run() task_work_run() |
| ____fput() ____fput() |
| perf_release() perf_release() |
| perf_event_release_kernel() perf_event_release_kernel() |
| _free_event() _free_event() |
| perf_pending_task_sync() perf_pending_task_sync() |
| rcuwait_wait_event() rcuwait_wait_event() |
| |
| Therefore the only option left is to acquire the event reference count |
| upon queueing the perf task work and release it from the task work, just |
| like it was done before 3a5465418f5f ("perf: Fix event leak upon exec and file release") |
| but without the leaks it fixed. |
| |
| Some adjustments are necessary to make it work: |
| |
| * A child event might dereference its parent upon freeing. Care must be |
| taken to release the parent last. |
| |
| * Some places assuming the event doesn't have any reference held and |
| therefore can be freed right away must instead put the reference and |
| let the reference counting to its job. |
| |
| The Linux kernel CVE team has assigned CVE-2025-37747 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.11 with commit 3a5465418f5fd970e86a86c7f4075be262682840 and fixed in 6.12.24 with commit fa1827fa968c0674e9b6fca223fa9fb4da4493eb |
| Issue introduced in 6.11 with commit 3a5465418f5fd970e86a86c7f4075be262682840 and fixed in 6.13.12 with commit 665b87b8f8b3aeb49083ef3b65c4953e7753fc12 |
| Issue introduced in 6.11 with commit 3a5465418f5fd970e86a86c7f4075be262682840 and fixed in 6.14.3 with commit 1267bd38f161c1a27d9b722de017027167a225a0 |
| Issue introduced in 6.11 with commit 3a5465418f5fd970e86a86c7f4075be262682840 and fixed in 6.15 with commit 56799bc035658738f362acec3e7647bb84e68933 |
| Issue introduced in 5.15.165 with commit 9ad46f1fef421d43cdab3a7d1744b2f43b54dae0 |
| Issue introduced in 6.1.103 with commit ed2c202dac55423a52d7e2290f2888bf08b8ee99 |
| Issue introduced in 6.6.44 with commit 104e258a004037bc7dba9f6085c71dad6af57ad4 |
| Issue introduced in 6.10.3 with commit f34d8307a73a18de5320fcc6f40403146d061891 |
| |
| 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-2025-37747 |
| 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: |
| include/linux/perf_event.h |
| kernel/events/core.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/fa1827fa968c0674e9b6fca223fa9fb4da4493eb |
| https://git.kernel.org/stable/c/665b87b8f8b3aeb49083ef3b65c4953e7753fc12 |
| https://git.kernel.org/stable/c/1267bd38f161c1a27d9b722de017027167a225a0 |
| https://git.kernel.org/stable/c/56799bc035658738f362acec3e7647bb84e68933 |
