Patch "x86/irq: Fix a race in x86_vector_free_irqs()" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

x86/irq: Fix a race in x86_vector_free_irqs()

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     x86-irq-fix-a-race-in-x86_vector_free_irqs.patch

and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jiang Liu <[email protected]>
Date: Thu, 31 Dec 2015 16:30:44 +0000
Subject: x86/irq: Fix a race in x86_vector_free_irqs()

From: Jiang Liu <[email protected]>

commit 111abeba67e0dbdc26537429de9155e4f1d807d8 upstream.

There's a race condition between

x86_vector_free_irqs()

{
	free_apic_chip_data(irq_data->chip_data);
	xxxxx	//irq_data->chip_data has been freed, but the pointer
		//hasn't been reset yet
	irq_domain_reset_irq_data(irq_data);
}

and

smp_irq_move_cleanup_interrupt()

{
	raw_spin_lock(&vector_lock);
	data = apic_chip_data(irq_desc_get_irq_data(desc));
	access data->xxxx	// may access freed memory
	raw_spin_unlock(&desc->lock);
}

which may cause smp_irq_move_cleanup_interrupt() to access freed memory.

Call irq_domain_reset_irq_data(), which clears the pointer with vector lock held.

[ tglx: Free memory outside of lock held region. ]

---
 arch/x86/kernel/apic/vector.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

@@ -224,10 +224,8 @@ static int assign_irq_vector_policy(int
 static void clear_irq_vector(int irq, struct apic_chip_data *data)
 {
 	struct irq_desc *desc;
-	unsigned long flags;
 	int cpu, vector;
 
-	raw_spin_lock_irqsave(&vector_lock, flags);
 	BUG_ON(!data->cfg.vector);
 
 	vector = data->cfg.vector;

@@ -237,10 +235,8 @@ static void clear_irq_vector(int irq, st
 	data->cfg.vector = 0;
 	cpumask_clear(data->domain);
 
-	if (likely(!data->move_in_progress)) {
-		raw_spin_unlock_irqrestore(&vector_lock, flags);
+	if (likely(!data->move_in_progress))
 		return;
-	}
 
 	desc = irq_to_desc(irq);
 	for_each_cpu_and(cpu, data->old_domain, cpu_online_mask) {

@@ -253,7 +249,6 @@ static void clear_irq_vector(int irq, st
 		}
 	}
 	data->move_in_progress = 0;
-	raw_spin_unlock_irqrestore(&vector_lock, flags);
 }
 
 void init_irq_alloc_info(struct irq_alloc_info *info,

@@ -274,19 +269,24 @@ void copy_irq_alloc_info(struct irq_allo
 static void x86_vector_free_irqs(struct irq_domain *domain,
 				 unsigned int virq, unsigned int nr_irqs)
 {
+	struct apic_chip_data *apic_data;
 	struct irq_data *irq_data;
+	unsigned long flags;
 	int i;
 
 	for (i = 0; i < nr_irqs; i++) {
 		irq_data = irq_domain_get_irq_data(x86_vector_domain, virq + i);
 		if (irq_data && irq_data->chip_data) {
+			raw_spin_lock_irqsave(&vector_lock, flags);
 			clear_irq_vector(virq + i, irq_data->chip_data);
-			free_apic_chip_data(irq_data->chip_data);
+			apic_data = irq_data->chip_data;
+			irq_domain_reset_irq_data(irq_data);
+			raw_spin_unlock_irqrestore(&vector_lock, flags);
+			free_apic_chip_data(apic_data);
 #ifdef	CONFIG_X86_IO_APIC
 			if (virq + i < nr_legacy_irqs())
 				legacy_irq_data[virq + i] = NULL;
 #endif
-			irq_domain_reset_irq_data(irq_data);
 		}
 	}
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/x86-irq-validate-that-irq-descriptor-is-still-active.patch queue-4.4/x86-irq-remove-outgoing-cpu-from-vector-cleanup-mask.patch queue-4.4/x86-irq-get-rid-of-code-duplication.patch queue-4.4/genirq-validate-action-before-dereferencing-it-in-handle_irq_event_percpu.patch queue-4.4/x86-irq-remove-offline-cpus-from-vector-cleanup.patch queue-4.4/x86-irq-reorganize-the-return-path-in-assign_irq_vector.patch queue-4.4/x86-irq-copy-vectormask-instead-of-an-and-operation.patch queue-4.4/x86-irq-call-irq_force_move_complete-with-irq-descriptor.patch queue-4.4/x86-irq-call-chip-irq_set_affinity-in-proper-context.patch queue-4.4/x86-irq-plug-vector-cleanup-race.patch queue-4.4/x86-irq-do-not-use-apic_chip_data.old_domain-as-temporary-buffer.patch queue-4.4/x86-irq-reorganize-the-search-in-assign_irq_vector.patch queue-4.4/x86-irq-remove-the-cpumask-allocation-from-send_cleanup_vector.patch queue-4.4/x86-irq-fix-a-race-in-x86_vector_free_irqs.patch queue-4.4/x86-irq-check-vector-allocation-early.patch queue-4.4/x86-irq-clear-move_in_progress-before-sending-cleanup-ipi.patch