CVE-2025-38687

/// Technical 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 detache

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References