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

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Summary

CVECVE-2026-64248
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-24 16:16:54 UTC
Updated2026-07-24 16:16:54 UTC
DescriptionIn 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_work.c:144 irq_work_queue_on ... rcu: INFO: rcu_sched detected stalls on CPUs/tasks: rcu: Offline CPU 1 blocking current GP. rcu: Offline CPU 2 blocking current GP. rcu: Offline CPU 3 blocking current GP. This issue was noticed on several Realtek MIPS switch SoCs (MIPS interAptiv) and came up during kernel bump downstream in OpenWrt from 6.18.33 to 6.18.34, after the backport of the patch to the 6.18 stable branch. The patch also has been backported all the way back to 6.1. Call rcutree_report_cpu_dead() once interrupts are disabled, mirroring the generic CPU-hotplug offline path, so RCU stops waiting on the parked CPUs and grace periods can still complete. MIPS shuts down all CPUs here without going through the CPU-hotplug mechanism, so this report is not otherwise issued. Reporting a dying CPU to RCU outside the regular hotplug offline path is not unprecedented: arm64 does the same in cpu_die_early(). There it is an exception for a CPU that was coming online and is aborting bringup, rather than the default shutdown action as on MIPS.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2dc79362302922cb18f35e262712b5e58de65442 f8a1ef884013dc99f712d3eb75624c7cd3fd94f6 git Not specified
CNA Linux Linux affected eef4f71b46a9929ac33e968538c9dd5d96a02460 e1919d026706544cb6e7251ec06e908edd6f34ee git Not specified
CNA Linux Linux affected 684a78183c54c23e70d1cba320f7fc184604210b 6eda71977ee11c222f8ad4cae4d18d50448e56f4 git Not specified
CNA Linux Linux affected 18c0456ea2615b1a743a6db739c74411c3b42bc6 f9b57a0015c241274651f4b36627f56b1b5a8651 git Not specified
CNA Linux Linux affected 91840be8f710370607f949a627e070896faeddb8 9fef09df42df55ab819b285ea892e0fc1b95a9c4 git Not specified
CNA Linux Linux affected 91840be8f710370607f949a627e070896faeddb8 9f3f3bdc6d9dac1a5a8262ee7ad0f2ff1527a7e7 git Not specified
CNA Linux Linux affected 81b582784518196eff1050212a046bc29d3a05dd git Not specified
CNA Linux Linux affected 6.1.175 6.1.178 semver Not specified
CNA Linux Linux affected 6.6.142 6.6.145 semver Not specified
CNA Linux Linux affected 6.12.92 6.12.95 semver Not specified
CNA Linux Linux affected 6.18.34 6.18.38 semver Not specified
CNA Linux Linux affected 7.0.11 7.1 semver Not specified
CNA Linux Linux affected 7.1 Not specified
CNA Linux Linux unaffected 7.1 semver Not specified
CNA Linux Linux unaffected 6.1.178 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.145 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.95 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.38 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.3 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/9f3f3bdc6d9dac1a5a8262ee7ad0f2ff1527a7e7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9fef09df42df55ab819b285ea892e0fc1b95a9c4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f8a1ef884013dc99f712d3eb75624c7cd3fd94f6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e1919d026706544cb6e7251ec06e908edd6f34ee 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f9b57a0015c241274651f4b36627f56b1b5a8651 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6eda71977ee11c222f8ad4cae4d18d50448e56f4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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