GHSA-5m9v-h8pg-4xv6

Описание

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

rcu/nocb: Fix rcuog wake-up from offline softirq

After a CPU has set itself offline and before it eventually calls rcutree_report_cpu_dead(), there are still opportunities for callbacks to be enqueued, for example from a softirq. When that happens on NOCB, the rcuog wake-up is deferred through an IPI to an online CPU in order not to call into the scheduler and risk arming the RT-bandwidth after hrtimers have been migrated out and disabled.

But performing a synchronized IPI from a softirq is buggy as reported in the following scenario:

Fix this with forcing deferred rcuog wake up through the NOCB timer when the CPU is offline. The actual wake up will happen from rcutree_report_cpu_dead().