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Message-ID: <2025090448-CVE-2025-38687-564a@gregkh> Date: Thu, 4 Sep 2025 17:32:52 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...nel.org> Subject: CVE-2025-38687: comedi: fix race between polling and detaching From: Greg Kroah-Hartman <gregkh@...nel.org> 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. The Linux kernel CVE team has assigned CVE-2025-38687 to this issue. Affected and fixed versions =========================== Issue introduced in 3.14 with commit 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 and fixed in 5.4.297 with commit fe67122ba781df44a1a9716eb1dfd751321ab512 Issue introduced in 3.14 with commit 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 and fixed in 5.10.241 with commit cd4286123d6948ff638ea9cd5818ae4796d5d252 Issue introduced in 3.14 with commit 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 and fixed in 5.15.190 with commit d85fac8729c9acfd72368faff1d576ec585e5c8f Issue introduced in 3.14 with commit 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 and fixed in 6.1.149 with commit 0f989f9d05492028afd2bded4b42023c57d8a76e Issue introduced in 3.14 with commit 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 and fixed in 6.6.103 with commit 5c4a2ffcbd052c69bbf4680677d4c4eaa5a252d4 Issue introduced in 3.14 with commit 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 and fixed in 6.12.43 with commit 017198079551a2a5cf61eae966af3c4b145e1f3b Issue introduced in 3.14 with commit 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 and fixed in 6.15.11 with commit 71ca60d2e631cf9c63bcbc7017961c61ff04e419 Issue introduced in 3.14 with commit 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 and fixed in 6.16.2 with commit 5724e82df4f9a4be62908362c97d522d25de75dd Issue introduced in 3.14 with commit 2f3fdcd7ce935f6f2899ceab57dc8fe5286db3e1 and fixed in 6.17-rc1 with commit 35b6fc51c666fc96355be5cd633ed0fe4ccf68b2 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2025-38687 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: drivers/comedi/comedi_fops.c drivers/comedi/comedi_internal.h drivers/comedi/drivers.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: 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
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