CVE-2025-38687 (GCVE-0-2025-38687)
Vulnerability from cvelistv5
Published
2025-09-04 15:32
Modified
2025-09-04 15:32
Severity ?
VLAI Severity ?
EPSS score ?
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
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| ▼ | Linux | Linux |
Version: 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 Version: 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 Version: 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 Version: 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 Version: 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 Version: 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 Version: 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 Version: 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 Version: 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 |
||||||
|
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"descriptions": [
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"lang": "en",
"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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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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{
"url": "https://git.kernel.org/stable/c/35b6fc51c666fc96355be5cd633ed0fe4ccf68b2"
}
],
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"datePublished": "2025-09-04T15:32:41.702Z",
"dateReserved": "2025-04-16T04:51:24.032Z",
"dateUpdated": "2025-09-04T15:32:41.702Z",
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}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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