[PATCH AUTOSEL 4.14 26/30] iommu/vt-d: Fix mm reference leak

Sasha Levin
2020-04-15T12:07:11Z

From: Jacob Pan <jacob.jun.pan@linux.intel.com>

[ Upstream commit 902baf61adf6b187f0a6b789e70d788ea71ff5bc ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 f5573bb9f450e..837459762eb39 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -613,14 +613,15 @@ 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)
--
2.20.1