From: Jiayuan Chen <jiayuan.chen@linux.dev> stable inclusion from stable-v6.6.142 commit eef4f71b46a9929ac33e968538c9dd5d96a02460 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16476 CVE: CVE-2026-64073 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 91840be8f710370607f949a627e070896faeddb8 ] On PREEMPT_RT, non-HARD irq_work runs in per-CPU kthreads via run_irq_workd(), so irq_work_sync() uses rcuwait() to wait for BUSY==0. After irq_work_single() clears BUSY via atomic_cmpxchg(), it still dereferences @work for irq_work_is_hard() and rcuwait_wake_up(). An irq_work_sync() caller on another CPU that enters after BUSY is cleared can observe BUSY==0 immediately, return, and free the work before those accesses complete — causing a use-after-free. Fix this by wrapping run_irq_workd() in guard(rcu)() so that the entire irq_work_single() execution is within an RCU read-side critical section. Then add synchronize_rcu() in irq_work_sync() after rcuwait_wait_event() to ensure the caller waits for the RCU grace period before returning, preventing premature frees. Fixes: 810979682ccc ("irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support.") Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev> Signed-off-by: Thomas Gleixner <tglx@kernel.org> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Link: https://patch.msgid.link/20260330073234.303732-1-jiayuan.chen@linux.dev Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> --- kernel/irq_work.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/irq_work.c b/kernel/irq_work.c index 2f4fb336dda1..188721af8eb3 100644 --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -292,6 +292,12 @@ void irq_work_sync(struct irq_work *work) !arch_irq_work_has_interrupt()) { rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work), TASK_UNINTERRUPTIBLE); + /* + * Ensure irq_work_single() does not access @work + * after removing IRQ_WORK_BUSY. It is always + * accessed within a RCU-read section. + */ + synchronize_rcu(); return; } @@ -302,6 +308,7 @@ EXPORT_SYMBOL_GPL(irq_work_sync); static void run_irq_workd(unsigned int cpu) { + guard(rcu)(); irq_work_run_list(this_cpu_ptr(&lazy_list)); } -- 2.34.1

From: Jonas Jelonek <jelonek.jonas@gmail.com> mainline inclusion from mainline-v7.2-rc1 commit 9f3f3bdc6d9dac1a5a8262ee7ad0f2ff1527a7e7 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16476 CVE: CVE-2026-64073 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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. Fixes: 91840be8f710 ("irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT") CC: stable@vger.kernel.org Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com> Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Conflcits: arch/mips/kernel/smp.c [ rcu_report_dead() has not renamed to rcutree_report_cpu_dead(). ] Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> --- arch/mips/kernel/smp.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c index 81f6c4f8fbc1..2ac945fae00a 100644 --- a/arch/mips/kernel/smp.c +++ b/arch/mips/kernel/smp.c @@ -19,6 +19,7 @@ #include <linux/sched/mm.h> #include <linux/cpumask.h> #include <linux/cpu.h> +#include <linux/rcupdate.h> #include <linux/err.h> #include <linux/ftrace.h> #include <linux/irqdomain.h> @@ -406,10 +407,12 @@ static void stop_this_cpu(void *dummy) /* * Remove this CPU: */ + int cpu = smp_processor_id(); - set_cpu_online(smp_processor_id(), false); + set_cpu_online(cpu, false); calculate_cpu_foreign_map(); local_irq_disable(); + rcu_report_dead(cpu); while (1); } -- 2.34.1