iommu/vt-d: Fix mm reference leak

Move canonical address check before mmget_not_zero() to avoid mm
reference leak.

Fixes: 9d8c3af31607 ("iommu/vt-d: IOMMU Page Request needs to check if address is canonical.")
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index d7f2a53..fc7d788 100644 (file)
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -611,14 +611,15 @@ static irqreturn_t prq_event_thread(int irq, void *d)
                 * any faults on kernel addresses. */
                if (!svm->mm)
                        goto bad_req;
-               /* If the mm is already defunct, don't handle faults. */
-               if (!mmget_not_zero(svm->mm))
-                       goto bad_req;
 
                /* If address is not canonical, return invalid response */
                if (!is_canonical_address(address))
                        goto bad_req;
 
+               /* If the mm is already defunct, don't handle faults. */
+               if (!mmget_not_zero(svm->mm))
+                       goto bad_req;
+
                down_read(&svm->mm->mmap_sem);
                vma = find_extend_vma(svm->mm, address);
                if (!vma || address < vma->vm_start)