CVE-2026-80866tipc: avoid busy looping in tipc_exit_net()

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/772769859226a5b004442403510acb58a1c32e72
• https://git.kernel.org/stable/c/99b82c8452887408ea908fdfa5df33c4a5dfa88f
• https://git.kernel.org/stable/c/110bb16d37bdba03213156c0df37e7119c190936
• https://git.kernel.org/stable/c/7672973957e3e20780afe5937a9fec70b72bc060
• https://git.kernel.org/stable/c/522d1d950b9e3b68190a6de7534827c8dccedb73
• https://git.kernel.org/stable/c/c1481c94e74c955e0448ddf46b8615a44d840c1e