[PATCH -next] iommu/arm-smmu: Fix missing unlock on error in arm_smmu_device_group()

[Yang Yingliang]

Add the missing unlock before return from function arm_smmu_device_group()
in the error handling case.

Fixes: b1a1347912a7 ("iommu/arm-smmu: Fix race condition during iommu_group creation")
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
---
 drivers/iommu/arm/arm-smmu/arm-smmu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 73893180ec7e..4bc75c4ce402 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1478,8 +1478,10 @@ static struct iommu_group *arm_smmu_device_group(struct device *dev)
 	mutex_lock(&smmu->stream_map_mutex);
 	for_each_cfg_sme(cfg, fwspec, i, idx) {
 		if (group && smmu->s2crs[idx].group &&
-		    group != smmu->s2crs[idx].group)
+		    group != smmu->s2crs[idx].group) {
+			mutex_unlock(&smmu->stream_map_mutex);
 			return ERR_PTR(-EINVAL);
+		}
 
 		group = smmu->s2crs[idx].group;
 	}
-- 
2.25.1