[Bugfix v2 3/5] x86/irq: Fix a race window in x86_vector_free_irqs()

[Jiang Liu]

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() accesses freed memory.
So use vector_lock to guard all memory free code in x86_vector_free_irqs().

Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/apic/vector.c |   20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index b32c6ef7b4b0..f648fce39d5e 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -228,23 +228,16 @@ static int assign_irq_vector_policy(int irq, int node,
 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);
+	int cpu, vector = data->cfg.vector;
 
-	vector = data->cfg.vector;
+	BUG_ON(!vector);
 	for_each_cpu_and(cpu, data->domain, cpu_online_mask)
 		per_cpu(vector_irq, cpu)[vector] = VECTOR_UNUSED;
-
 	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) {
@@ -257,7 +250,7 @@ static void clear_irq_vector(int irq, struct apic_chip_data *data)
 		}
 	}
 	data->move_in_progress = 0;
-	raw_spin_unlock_irqrestore(&vector_lock, flags);
+	cpumask_clear(data->old_domain);
 }
 
 void init_irq_alloc_info(struct irq_alloc_info *info,
@@ -279,18 +272,21 @@ static void x86_vector_free_irqs(struct irq_domain *domain,
 				 unsigned int virq, unsigned int nr_irqs)
 {
 	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);
+			irq_domain_reset_irq_data(irq_data);
+			raw_spin_unlock_irqrestore(&vector_lock, flags);
 #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);
 		}
 	}
 }
-- 
1.7.10.4

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