CVE-2022-50833

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->cmdwork work from systemwq 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 queuework(hdev->workqueue). Also, protect the queuing operation with RCU read lock in order to avoid calling queuedelayedwork() after canceldelayedwork() completed.