[PATCH 2/2] dma-buf: handle empty dma_fence_arrays gracefully

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

A bug inside the new sync-file merge code created empty dma_fence_array instances.

Warn about that and handle those without crashing.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-fence-array.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
index 52b85d292383..5c8a7084577b 100644
--- a/drivers/dma-buf/dma-fence-array.c
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -159,6 +159,8 @@ struct dma_fence_array *dma_fence_array_create(int num_fences,
 	struct dma_fence_array *array;
 	size_t size = sizeof(*array);
 
+	WARN_ON(!num_fences || !fences);
+
 	/* Allocate the callback structures behind the array. */
 	size += num_fences * sizeof(struct dma_fence_array_cb);
 	array = kzalloc(size, GFP_KERNEL);
@@ -231,6 +233,9 @@ struct dma_fence *dma_fence_array_first(struct dma_fence *head)
 	if (!array)
 		return head;
 
+	if (!array->num_fences)
+		return NULL;
+
 	return array->fences[0];
 }
 EXPORT_SYMBOL(dma_fence_array_first);
-- 
2.25.1