CVE-2026-53180

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

timers/migration: Fix livelock in tmigr_handle_remote_up()

tmigr_handle_remote_cpu() skips timer_expire_remote() when cpu == smp_processor_id(), assuming the local softirq path already handled this CPUs timers.

This assumption is wrong because jiffies can advance after the handling of the CPUs global timers in run_timer_base(BASE_GLOBAL) and before tmigr_handle_remote() evaluates the expiry times.

As a consequence a timer which expires after the CPU local timer wheel advanced and becomes expired in the remote handling is ignored and the callback is never invoked and removed from the timer wheel.

Whats worse is that fetch_next_timer_interrupt_remote() keeps reporting it as expired, and the event is re-queued with expires == now on each iteration. The goto-again loop spins indefinitely.

Fix this by calling timer_expire_remote() unconditionally. Thats minimal overhead for the common case as __run_timer_base() returns immediately if there is nothing to expire in the local wheel.

[ tglx: Amend change log and add a comment ]

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/07b3b83587fb3012619f4439389b64a955fc7836
• https://git.kernel.org/stable/c/1d6c2062b77be09ec15d6bf637b2e2221c4482fc
• https://git.kernel.org/stable/c/d338e61ea94052a786aac9f58e9f0d8520afa0fd
• https://git.kernel.org/stable/c/d486b4934a8e504376b85cdb3766f306d57aff5b