[PATCH 2/3] iommu/vt-d: Fix mm reference leak

From: Jacob Pan
Date: Fri Mar 20 2020 - 00:27:03 EST


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@xxxxxxxxxxxxxxx>
---
drivers/iommu/intel-svm.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index 1483f1845762..56253c59ca10 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -861,14 +861,15 @@ 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)
--
2.7.4