CVE-2026-80866
Received Received - Intake

TIPC Net Exit Busy Loop in Linux Kernel

Publication date: 2026-09-04

Last updated on: 2026-09-04

Assigner: kernel.org

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.

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Meta Information

Published
2026-09-04
Last Modified
2026-09-04
Generated
2026-09-05
AI Q&A
2026-09-04
EPSS Evaluated
N/A
NVD
CVE-2026-80866
EUVD
EUVD-2026-71496

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a busy-wait loop in the TIPC (Transparent Inter-Process Communication) module's network namespace exit function. The loop waits for pending UDP bearer cleanup tasks to complete but can run indefinitely if the task has high priority or the kernel lacks preemption support. This wastes CPU cycles and may cause soft lockups.

Detection Guidance

This vulnerability may cause high CPU usage or soft lockups during network namespace cleanup. Monitor for processes stuck in 'D' state or excessive CPU usage by kernel threads. Check system logs for messages about tipc or netns operations. Use 'top' or 'htop' to observe CPU spikes and 'dmesg' for kernel warnings.

Impact Analysis

The vulnerability can lead to system performance degradation due to excessive CPU usage from the busy-wait loop. In severe cases, it may cause the system to become unresponsive or trigger kernel watchdogs, resulting in soft lockups that disrupt normal operations.

Mitigation Strategies

Apply the Linux kernel patch that replaces the busy-wait loop with wait_var_event(). Update to a kernel version containing the fix. If immediate patching is not possible, avoid high-priority tasks during network namespace exits or disable TIPC module if unused. Monitor system performance until patched.

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