CVE-2026-53180

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

timers/migration: Fix livelock in tmigrhandleremote_up()

tmigrhandleremotecpu() skips timerexpireremote() when cpu == smpprocessor_id(), assuming the local softirq path already handled this CPU's timers.

This assumption is wrong because jiffies can advance after the handling of the CPU's global timers in runtimerbase(BASEGLOBAL) and before tmigrhandle_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.

What's worse is that fetchnexttimerinterruptremote() 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 timerexpireremote() unconditionally. That's minimal overhead for the common case as __runtimerbase() returns immediately if there is nothing to expire in the local wheel.

[ tglx: Amend change log and add a comment ]