[Bugfix 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....@linux.intel.com>
---
 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 f03957e7c50d..57934ef1d032 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -231,23 +231,16 @@ 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) {
@@ -260,7 +253,7 @@ 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,
@@ -282,18 +275,21 @@ 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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