[PATCH v2 2/2] iommu/arm-smmu-v3: don't unregister on shutdown

[Vladimir Oltean]

Similar to SMMUv2, this driver calls iommu_device_unregister() from the
shutdown path, which removes the IOMMU groups with no coordination
whatsoever with their users - shutdown methods are optional in device
drivers. This can lead to NULL pointer dereferences in those drivers'
DMA API calls, or worse.

Instead of calling the full arm_smmu_device_remove() from
arm_smmu_device_shutdown(), let's pick only the relevant function call -
arm_smmu_device_disable() - more or less the reverse of
arm_smmu_device_reset() - and call just that from the shutdown path.

Fixes: 57365a04c921 ("iommu: Move bus setup to IOMMU device registration")
Suggested-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
---
v1->v2: patch is new

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 6d5df91c5c46..d4d8bfee9feb 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3854,7 +3854,9 @@ static int arm_smmu_device_remove(struct platform_device *pdev)
 
 static void arm_smmu_device_shutdown(struct platform_device *pdev)
 {
-	arm_smmu_device_remove(pdev);
+	struct arm_smmu_device *smmu = platform_get_drvdata(pdev);
+
+	arm_smmu_device_disable(smmu);
 }
 
 static const struct of_device_id arm_smmu_of_match[] = {
-- 
2.34.1