CVE-2026-80866

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CVE-2026-80866

Summary: tipc: avoid busy looping in tipc_exit_net()

Details: 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.

References: https://git.kernel.org/stable/c/522d1d950b9e3b68190a6de7534827c8dccedb73, https://git.kernel.org/stable/c/c1481c94e74c955e0448ddf46b8615a44d840c1e, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80866.json, https://nvd.nist.gov/vuln/detail/CVE-2026-80866, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git