comedi: fix race between polling and detaching

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-38687
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-09-04 16:15:36 UTC
Updated2026-05-12 13:16:55 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 4.7 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-362

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 fe67122ba781df44a1a9716eb1dfd751321ab512 git Not specified
CNA Linux Linux affected 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 cd4286123d6948ff638ea9cd5818ae4796d5d252 git Not specified
CNA Linux Linux affected 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 d85fac8729c9acfd72368faff1d576ec585e5c8f git Not specified
CNA Linux Linux affected 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 0f989f9d05492028afd2bded4b42023c57d8a76e git Not specified
CNA Linux Linux affected 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 5c4a2ffcbd052c69bbf4680677d4c4eaa5a252d4 git Not specified
CNA Linux Linux affected 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 017198079551a2a5cf61eae966af3c4b145e1f3b git Not specified
CNA Linux Linux affected 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 71ca60d2e631cf9c63bcbc7017961c61ff04e419 git Not specified
CNA Linux Linux affected 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 5724e82df4f9a4be62908362c97d522d25de75dd git Not specified
CNA Linux Linux affected 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 35b6fc51c666fc96355be5cd633ed0fe4ccf68b2 git Not specified
CNA Linux Linux affected 3.14 Not specified
CNA Linux Linux unaffected 3.14 semver Not specified
CNA Linux Linux unaffected 5.4.297 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.241 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.190 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.149 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.103 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.43 6.12.* semver Not specified
CNA Linux Linux unaffected 6.15.11 6.15.* semver Not specified
CNA Linux Linux unaffected 6.16.2 6.16.* semver Not specified
CNA Linux Linux unaffected 6.17 * original_commit_for_fix Not specified
ADP Siemens SIMATIC CN 4100 affected V5.0 custom Not specified

References

ReferenceSourceLinkTags
lists.debian.org/debian-lts-announce/2025/10/msg00008.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Third Party Advisory
git.kernel.org/stable/c/cd4286123d6948ff638ea9cd5818ae4796d5d252 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/017198079551a2a5cf61eae966af3c4b145e1f3b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/5c4a2ffcbd052c69bbf4680677d4c4eaa5a252d4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/35b6fc51c666fc96355be5cd633ed0fe4ccf68b2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/0f989f9d05492028afd2bded4b42023c57d8a76e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/d85fac8729c9acfd72368faff1d576ec585e5c8f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/5724e82df4f9a4be62908362c97d522d25de75dd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-032379.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/fe67122ba781df44a1a9716eb1dfd751321ab512 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/10/msg00007.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Third Party Advisory
git.kernel.org/stable/c/71ca60d2e631cf9c63bcbc7017961c61ff04e419 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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