tipc: avoid busy looping in tipc_exit_net()

Summary

In the Linux kernel, the following vulnerability has been resolved: tipc: avoid busy looping in tipc_exit_net() Blamed commit introduced a busy-wait loop in tipc_exit_net() to wait for pending UDP bearer cleanup works to complete: while (atomic_read(&tn->wq_count)) cond_resched(); This loop can busy-wait for a long time if cond_resched() is a NOP. This typically happens if the netns exit is executed by a high priority task, or under kernels configured without preemption (CONFIG_PREEMPT_NONE). In such cases, it wastes CPU cycles and can lead to soft lockups. Fix this by replacing the busy loop with wait_var_event(), allowing the thread to sleep properly until the work queue count reaches zero. Accordingly, update cleanup_bearer() to use atomic_dec_and_test() and wake_up_var() to wake up the waiter when the count drops to zero. This uses the global wait queue hash table, avoiding the need to bloat struct tipc_net with a wait_queue_head_t. The atomic_dec_and_test() provides the necessary memory barrier to ensure the wakeup is not missed.

Timeline

1. Sep 4, 2026, 4:48 PM UTCCVE published
2. Oct 21, 2026, 12:47 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 04c26faa51d1e2fe71cf13c45791f5174c37f986 · fixed in 99b82c8452887408ea908fdfa5df33c4a5dfa88f; From 04c26faa51d1e2fe71cf13c45791f5174c37f986 · fixed in 110bb16d37bdba03213156c0df37e7119c190936; From 04c26faa51d1e2fe71cf13c45791f5174c37f986 · fixed in 7672973957e3e20780afe5937a9fec70b72bc060; From 04c26faa51d1e2fe71cf13c45791f5174c37f986 · fixed in 522d1d950b9e3b68190a6de7534827c8dccedb73; From 04c26faa51d1e2fe71cf13c45791f5174c37f986 · fixed in c1481c94e74c955e0448ddf46b8615a44d840c1e; From 5.4.124 · fixed in 5.5; From 5.10.42 · fixed in 5.11; From 5.12.9 · fixed in 5.13

• Linux Linux

  5.13

• KernelLinux

  From 5.13.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.114; From 6.13.0 · fixed in 6.18.57; From 6.19.0 · fixed in 7.1.5

References 5