CVE-2026-64248

/// Technical description

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

MIPS: smp: report dying CPU to RCU in stop_this_cpu()

smp_send_stop() parks all secondary CPUs in stop_this_cpu(). The function

marks the CPU offline for the scheduler via set_cpu_online(false) but

never informs RCU, so RCU keeps expecting a quiescent state from CPUs

that are now spinning forever with interrupts disabled.

As long as nothing waits for an RCU grace period after smp_send_stop()

this is harmless, which is why it went unnoticed. Since commit

91840be8f710 ("irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT")

however, irq_work_sync() calls synchronize_rcu() on architectures without

an irq_work self-IPI, i.e. where arch_irq_work_has_interrupt() returns

false. That is the asm-generic default used by MIPS. Any irq_work_sync()

issued in the reboot/shutdown path after smp_send_stop() then blocks on

a grace period that can never complete, hanging the reboot:

WARNING: CPU: 0 PID: 15 at kernel/irq

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References