vfio/type1: Fix leak on error path

We also don't handle unpinning zero pages as an error on other exits
so we can fix that inconsistency by rolling in the next conditional
return.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio_iommu_type1.c

@@ -436,6 +436,12 @@ static int vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
 	}
 
 	/* Split existing */
+
+	/*
+	 * Allocate our tracking structure early even though it may not
+	 * be used.  An Allocation failure later loses track of pages and
+	 * is more difficult to unwind.
+	 */
 	split = kzalloc(sizeof(*split), GFP_KERNEL);
 	if (!split)
 		return -ENOMEM;
@@ -443,12 +449,9 @@ static int vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
 	offset = start - dma->iova;
 
 	ret = vfio_unmap_unpin(iommu, dma, start, size);
-	if (ret)
-		return ret;
-
-	if (!*size) {
+	if (ret || !*size) {
 		kfree(split);
-		return -EINVAL;
+		return ret;
 	}
 
 	tmp = dma->size;