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.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 to < fe67122ba781df44a1a9716eb1dfd751321ab512affected2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 to < cd4286123d6948ff638ea9cd5818ae4796d5d252affected2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 to < d85fac8729c9acfd72368faff1d576ec585e5c8faffected2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 to < 0f989f9d05492028afd2bded4b42023c57d8a76eaffected2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 to < 5c4a2ffcbd052c69bbf4680677d4c4eaa5a252d4affected2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 to < 017198079551a2a5cf61eae966af3c4b145e1f3baffected2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 to < 71ca60d2e631cf9c63bcbc7017961c61ff04e419affected2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 to < 5724e82df4f9a4be62908362c97d522d25de75ddaffected2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 to < 35b6fc51c666fc96355be5cd633ed0fe4ccf68b2affected
Linux Linux
Default version status: affected
3.14affected0 to < 3.14unaffected5.4.297 to ≤ 5.4.*unaffected5.10.241 to ≤ 5.10.*unaffected5.15.190 to ≤ 5.15.*unaffected6.1.149 to ≤ 6.1.*unaffected6.6.103 to ≤ 6.6.*unaffected6.12.43 to ≤ 6.12.*unaffected6.15.11 to ≤ 6.15.*unaffected6.16.2 to ≤ 6.16.*unaffected6.17 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/fe67122ba781df44a1a9716eb1dfd751321ab512 ↗
- https://git.kernel.org/stable/c/cd4286123d6948ff638ea9cd5818ae4796d5d252 ↗
- https://git.kernel.org/stable/c/d85fac8729c9acfd72368faff1d576ec585e5c8f ↗
- https://git.kernel.org/stable/c/0f989f9d05492028afd2bded4b42023c57d8a76e ↗
- https://git.kernel.org/stable/c/5c4a2ffcbd052c69bbf4680677d4c4eaa5a252d4 ↗
- https://git.kernel.org/stable/c/017198079551a2a5cf61eae966af3c4b145e1f3b ↗
- https://git.kernel.org/stable/c/71ca60d2e631cf9c63bcbc7017961c61ff04e419 ↗
- https://git.kernel.org/stable/c/5724e82df4f9a4be62908362c97d522d25de75dd ↗
- https://git.kernel.org/stable/c/35b6fc51c666fc96355be5cd633ed0fe4ccf68b2 ↗
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html ↗
- https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html ↗
- https://cert-portal.siemens.com/productcert/html/ssa-032379.html ↗