[PATCH v2] iommu/vt-d: race setting IRQ CPU affinity while freeing IRQ

Greg Edwards
2014-07-23T16:13:31Z

A user process setting the CPU affinity of an IRQ for a KVM
direct-assigned device via /proc/irq/<IRQ#>/smp_affinity can race with
the IRQ being released by QEMU, resulting in a NULL iommu pointer
dereference in get_irte().

Signed-off-by: Greg Edwards <gedwards@ddn.com>
---

Dropped the Cc: for stable since this likely wouldn't ever be seen in
the real world. We saw it on an automated CI stress test.

drivers/iommu/intel_irq_remapping.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index 9b17489..d926676 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -70,6 +70,11 @@ static int get_irte(int irq, struct irte *entry)

raw_spin_lock_irqsave(&irq_2_ir_lock, flags);

+ 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