in function iommu_support_dev_iotlb(),return value of device_to_iommu()
is used without checking, this could cause NULL pointer issue.

this patch is for v3.12.6

Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
---
  drivers/iommu/intel-iommu.c |    2 ++
  1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 40203ad..5b4531a 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1105,6 +1105,8 @@ static struct device_domain_info 
*iommu_support_dev_iotlb(
      struct device_domain_info *info;
      struct intel_iommu *iommu = device_to_iommu(segment, bus, devfn);

+    if (!iommu)
+        return NULL;
      if (!ecap_dev_iotlb_support(iommu->ecap))
          return NULL;

-- 
1.7.1