[PATCH] vfio_iommu_type1: increase the validity check of function parameters

[Li kunyu]

Added validity check for count variable, return if count variable does 
not meet the execution condition (do not execute mutex_lock and 
mutex_unlock function).

Signed-off-by: Li kunyu <kunyu@xxxxxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 23c24fe98c00..9bdf96d932e4 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -3137,6 +3137,9 @@ static int vfio_iommu_type1_dma_rw(void *iommu_data, dma_addr_t user_iova,
 	int ret = 0;
 	size_t done;
 
+	if (count <= 0)
+		return ret;
+
 	mutex_lock(&iommu->lock);
 	while (count > 0) {
 		ret = vfio_iommu_type1_dma_rw_chunk(iommu, user_iova, data,
-- 
2.18.2