[PATCH] iommu/vt-d: fix race between free_irte() and get_irte()

[Greg Edwards]

get_irte() can race with free_irte() and dereference a NULL iommu
pointer.

Signed-off-by: Greg Edwards <gedwards@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 drivers/iommu/intel_irq_remapping.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index 9b17489..2d67e6d 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -70,6 +70,12 @@ static int get_irte(int irq, struct irte *entry)
 
 	raw_spin_lock_irqsave(&irq_2_ir_lock, flags);
 
+	/* ensure we're not racing with free_irte() */
+	if (unlikely(!irq_iommu->iommu)) {
+		raw_spin_unlock_irqrestore(&irq_2_ir_lock, flags);
+		return -1;
+	}
+
 	index = irq_iommu->irte_index + irq_iommu->sub_handle;
 	*entry = *(irq_iommu->iommu->ir_table->base + index);
 
-- 
1.9.3

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