CVE-2026-98342dmaengine: wait for RCU readers before releasing dma_device

Official description

In the Linux kernel, the following vulnerability has been resolved: dmaengine: wait for RCU readers before releasing dma_device dma_issue_pending_all() walks the dma_device_list with list_for_each_entry_rcu() under rcu_read_lock(). dma_device_release() unlinks the device with list_del_rcu() and then calls device->device_release() (which in many drivers, such as plx_dma.c, directly calls kfree()). Because there is no grace period between unlinking the device and freeing it, concurrent RCU readers in dma_issue_pending_all() can access the device after it has been freed. The lockless walk originally relied on clients holding a dmaengine reference to pin the provider module, and therefore the device, for as long as they might traverse the list. Commit 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct") decoupled the dma_device lifetime from the module reference, so the device can now be released while a reader is still walking the list. Add synchronize_rcu() before the device is freed, so RCU readers are guaranteed to have finished. Keep it unconditional: providers that do not implement device_release() free the device themselves once dma_async_device_unregister() returns. This call will delay for a grace period with dma_list_mutex held, which is safe and only teardown path is delayed.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/ac8ce9f89638d6d79875cca7d8ae42566a9bde15
• https://git.kernel.org/stable/c/14578c78405d51fa92e4ada4502a45f537c0fcb8
• https://git.kernel.org/stable/c/cbb3310a5167e868a5e763e32b9a23b4d50669ee
• https://git.kernel.org/stable/c/8577a5ec4f7e00443015ef99f646def093121a1b
• https://git.kernel.org/stable/c/4448a539a0c39141cccc67be6cacde0f35024313
• https://git.kernel.org/stable/c/fc1f4884f1d46fc7a8cee6e2997ecc9e8d1c7f77
• https://git.kernel.org/stable/c/4aed7e47a10b94ea3c5171e8d1382081accd2e03
• https://git.kernel.org/stable/c/dc750422170a563c7a81f6e49d36bb02c62ae37f