Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: use hdev->workqueue when queuing hdev->{cmd,ncmd}_timer works syzbot is reporting attempt to schedule hdev->cmd_work work from system_wq WQ into hdev->workqueue WQ which is under draining operation [1], for commit c8efcc2589464ac7 ("workqueue: allow chained queueing during destruction") does not allow such operation. The check introduced by commit 877afadad2dce8aa ("Bluetooth: When HCI work queue is drained, only queue chained work") was incomplete. Use hdev->workqueue WQ when queuing hdev->{cmd,ncmd}_timer works because hci_{cmd,ncmd}_timeout() calls queue_work(hdev->workqueue). Also, protect the queuing operation with RCU read lock in order to avoid calling queue_delayed_work() after cancel_delayed_work() completed.

References 3

• git.kernel.org https://git.kernel.org/stable/c/3c6b036fe5c8ed8b6c4cbdc03605929882907ef0
• git.kernel.org https://git.kernel.org/stable/c/c4635cf3d845a7324c25c52d549b70c8bd7ad4c7
• git.kernel.org https://git.kernel.org/stable/c/deee93d13d385103205879a8a0915036ecd83261

Remediation