CVE-2025-38687
Description
In the Linux kernel, the following vulnerability has been resolved: comedi: fix race between polling and detaching syzbot reports a use-after-free in comedi in the below link, which is due to comedi gladly removing the allocated async area even though poll requests are still active on the wait_queue_head inside of it. This can cause a use-after-free when the poll entries are later triggered or removed, as the memory for the wait_queue_head has been freed. We need to check there are no tasks queued on any of the subdevices' wait queues before allowing the device to be detached by the `COMEDI_DEVCONFIG` ioctl. Tasks will read-lock `dev->attach_lock` before adding themselves to the subdevice wait queue, so fix the problem in the `COMEDI_DEVCONFIG` ioctl handler by write-locking `dev->attach_lock` before checking that all of the subdevices are safe to be deleted. This includes testing for any sleepers on the subdevices' wait queues. It remains locked until the device has been detached. This requires the `comedi_device_detach()` function to be refactored slightly, moving the bulk of it into new function `comedi_device_detach_locked()`. Note that the refactor of `comedi_device_detach()` results in `comedi_device_cancel_all()` now being called while `dev->attach_lock` is write-locked, which wasn't the case previously, but that does not matter. Thanks to Jens Axboe for diagnosing the problem and co-developing this patch.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| sles | affected | | |
| debian | bookworm | fixed | 6.1.153-1 |
| debian | bullseye | fixed | 5.10.244-1 |
| debian | forky | fixed | 6.16.3-1 |
| debian | sid | fixed | 6.16.3-1 |
| debian | trixie | fixed | 6.12.43-1 |
| linux-kernel | affected | 5.4.297 | |
| debian | 11.0 | affected | |
References
- https://git.kernel.org/stable/c/017198079551a2a5cf61eae966af3c4b145e1f3b
- https://git.kernel.org/stable/c/0f989f9d05492028afd2bded4b42023c57d8a76e
- https://git.kernel.org/stable/c/35b6fc51c666fc96355be5cd633ed0fe4ccf68b2
- https://git.kernel.org/stable/c/5724e82df4f9a4be62908362c97d522d25de75dd
- https://git.kernel.org/stable/c/5c4a2ffcbd052c69bbf4680677d4c4eaa5a252d4
- https://git.kernel.org/stable/c/71ca60d2e631cf9c63bcbc7017961c61ff04e419
- https://git.kernel.org/stable/c/cd4286123d6948ff638ea9cd5818ae4796d5d252
- https://git.kernel.org/stable/c/d85fac8729c9acfd72368faff1d576ec585e5c8f
- https://git.kernel.org/stable/c/fe67122ba781df44a1a9716eb1dfd751321ab512
- https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
- https://cert-portal.siemens.com/productcert/html/ssa-032379.html
- https://www.suse.com/security/cve/CVE-2025-38687.html
- https://security-tracker.debian.org/tracker/CVE-2025-38687
CWEs
CWE-362
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.