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.
Product status
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (git) before fe67122ba781df44a1a9716eb1dfd751321ab512
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (git) before cd4286123d6948ff638ea9cd5818ae4796d5d252
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (git) before d85fac8729c9acfd72368faff1d576ec585e5c8f
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (git) before 0f989f9d05492028afd2bded4b42023c57d8a76e
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (git) before 5c4a2ffcbd052c69bbf4680677d4c4eaa5a252d4
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (git) before 017198079551a2a5cf61eae966af3c4b145e1f3b
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (git) before 71ca60d2e631cf9c63bcbc7017961c61ff04e419
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (git) before 5724e82df4f9a4be62908362c97d522d25de75dd
2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 (git) before 35b6fc51c666fc96355be5cd633ed0fe4ccf68b2
3.14
Any version before 3.14
5.4.297 (semver)
5.10.241 (semver)
5.15.190 (semver)
6.1.149 (semver)
6.6.103 (semver)
6.12.43 (semver)
6.15.11 (semver)
6.16.2 (semver)
6.17 (original_commit_for_fix)
References
git.kernel.org/...c/fe67122ba781df44a1a9716eb1dfd751321ab512
git.kernel.org/...c/cd4286123d6948ff638ea9cd5818ae4796d5d252
git.kernel.org/...c/d85fac8729c9acfd72368faff1d576ec585e5c8f
git.kernel.org/...c/0f989f9d05492028afd2bded4b42023c57d8a76e
git.kernel.org/...c/5c4a2ffcbd052c69bbf4680677d4c4eaa5a252d4
git.kernel.org/...c/017198079551a2a5cf61eae966af3c4b145e1f3b
git.kernel.org/...c/71ca60d2e631cf9c63bcbc7017961c61ff04e419
git.kernel.org/...c/5724e82df4f9a4be62908362c97d522d25de75dd
git.kernel.org/...c/35b6fc51c666fc96355be5cd633ed0fe4ccf68b2
