CVE-2021-47163

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

tipc: wait and exit until all work queues are done

On some host, a crash could be triggered simply by repeating these

commands several times:

# modprobe tipc

# tipc bearer enable media udp name UDP1 localip 127.0.0.1

# rmmod tipc

[] BUG: unable to handle kernel paging request at ffffffffc096bb00

[] Workqueue: events 0xffffffffc096bb00

[] Call Trace:

[] ? process_one_work+0x1a7/0x360

[] ? worker_thread+0x30/0x390

[] ? create_worker+0x1a0/0x1a0

[] ? kthread+0x116/0x130

[] ? kthread_flush_work_fn+0x10/0x10

[] ? ret_from_fork+0x35/0x40

When removing the TIPC module, the UDP tunnel sock will be delayed to

release in a work queue as sock_release() can't be done in rtnl_lock().

If the work queue is schedule to run after the TIPC module is removed,

kernel will crash as the work queue function cleanup_beareri() code no

longer exists when trying to invoke it.

To fix it, this patch introduce a

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References