FKIE_CVE-2025-38687

Vulnerability from fkie_nvd - Published: 2025-09-04 16:15 - Updated: 2026-01-09 19:00
Severity ?
4.7 (Medium) - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/017198079551a2a5cf61eae966af3c4b145e1f3bPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0f989f9d05492028afd2bded4b42023c57d8a76ePatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/35b6fc51c666fc96355be5cd633ed0fe4ccf68b2Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5724e82df4f9a4be62908362c97d522d25de75ddPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5c4a2ffcbd052c69bbf4680677d4c4eaa5a252d4Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/71ca60d2e631cf9c63bcbc7017961c61ff04e419Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cd4286123d6948ff638ea9cd5818ae4796d5d252Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d85fac8729c9acfd72368faff1d576ec585e5c8fPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/fe67122ba781df44a1a9716eb1dfd751321ab512Patch
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2025/10/msg00007.htmlThird Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlThird Party Advisory
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
debian debian_linux 11.0
To clipboard 

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncomedi: fix race between polling and detaching\n\nsyzbot reports a use-after-free in comedi in the below link, which is\ndue to comedi gladly removing the allocated async area even though poll\nrequests are still active on the wait_queue_head inside of it. This can\ncause a use-after-free when the poll entries are later triggered or\nremoved, as the memory for the wait_queue_head has been freed.  We need\nto check there are no tasks queued on any of the subdevices\u0027 wait queues\nbefore allowing the device to be detached by the `COMEDI_DEVCONFIG`\nioctl.\n\nTasks will read-lock `dev-\u003eattach_lock` before adding themselves to the\nsubdevice wait queue, so fix the problem in the `COMEDI_DEVCONFIG` ioctl\nhandler by write-locking `dev-\u003eattach_lock` before checking that all of\nthe subdevices are safe to be deleted.  This includes testing for any\nsleepers on the subdevices\u0027 wait queues.  It remains locked until the\ndevice has been detached.  This requires the `comedi_device_detach()`\nfunction to be refactored slightly, moving the bulk of it into new\nfunction `comedi_device_detach_locked()`.\n\nNote that the refactor of `comedi_device_detach()` results in\n`comedi_device_cancel_all()` now being called while `dev-\u003eattach_lock`\nis write-locked, which wasn\u0027t the case previously, but that does not\nmatter.\n\nThanks to Jens Axboe for diagnosing the problem and co-developing this\npatch."
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  "id": "CVE-2025-38687",
  "lastModified": "2026-01-09T19:00:55.593",
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