tipc: destroy topsrv workqueues before closing connections

Overview

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

tipc: destroy topsrv workqueues before closing connections

tipc_topsrv_stop() closed subscriber connections while the topology server's send and receive workqueues were still running. Socket callbacks and subscription events could then queue more work, and in-flight send/recv work could drop the last connection reference during the conn_idr walk.

That race produced several teardown failures: refcount_t addition on 0 from conn_get() on a connection whose release was blocked on idr_lock, a subsequent use-after-free in tipc_conn_close(), queue_work() on an already destroyed workqueue from the listener data-ready callback, and an RCU stall in tipc_topsrv_exit_net() while the walk spun under idr_lock.

Clear srv->listener under idr_lock so it acts as a shutdown flag, skip queue_work() once it is NULL, destroy the workqueues to flush in-flight work, and only then close the remaining connections. Refuse tipc_conn_lookup() after that flag is cleared, and drop idr_lock when the teardown walk finds no connection, so an in-flight subscription event cannot pin idr_in_use while the walk holds the lock.

v3 supersedes the narrower in-thread diff Tung Quang Nguyen posted on 2026-09-23. It keeps his teardown order and adds the lookup refusal and the empty-idr unlock.

Affected

• Linux >= c5fa7b3cf3cb22e4ac60485fc2dc187fe012910f < 7f796bb3b440d7f1b14c0e3b520462eb34f553af
• Linux >= c5fa7b3cf3cb22e4ac60485fc2dc187fe012910f < da9c16568bc79140a54c1f5fcf07a0305df47b37
• Linux >= c5fa7b3cf3cb22e4ac60485fc2dc187fe012910f < 0af8780bdfdfc91fb9127bddb9c48fab67dc9d9e
• Linux >= c5fa7b3cf3cb22e4ac60485fc2dc187fe012910f < fb717c536af2aafeca520ff11d1e0f25f7ab8fa9
• Linux >= c5fa7b3cf3cb22e4ac60485fc2dc187fe012910f < 3acdd44385bc7e2e57605e073691ce69cc5a960d
• Linux 3.11

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.