Re: [PATCH] virtio_ring: check desc == NULL when packed and indirect

In the case of packed, use indirect desc, since desc is allocated by
kmalloc_array(), we should check whether its return value is NULL.

Fixes: 1ce9e6055fa ("virtio_ring: introduce packed ring support")
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index dd95dfd85e98..7dd381eae725 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c

@@ -1050,21 +1050,20 @@ static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
 }
 
 static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
-				       struct scatterlist *sgs[],
-				       unsigned int total_sg,
-				       unsigned int out_sgs,
-				       unsigned int in_sgs,
-				       void *data,
-				       gfp_t gfp)
+					 struct scatterlist *sgs[],
+					 struct vring_packed_desc *desc,
+					 unsigned int total_sg,
+					 unsigned int out_sgs,
+					 unsigned int in_sgs,
+					 void *data,
+					 gfp_t gfp)
 {
-	struct vring_packed_desc *desc;
 	struct scatterlist *sg;
 	unsigned int i, n, err_idx;
 	u16 head, id;
 	dma_addr_t addr;
 
 	head = vq->packed.next_avail_idx;
-	desc = alloc_indirect_packed(total_sg, gfp);
 
 	if (unlikely(vq->vq.num_free < 1)) {
 		pr_debug("Can't add buf len 1 - avail = 0\n");

@@ -1191,9 +1190,15 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 
 	BUG_ON(total_sg == 0);
 
-	if (virtqueue_use_indirect(_vq, total_sg))
-		return virtqueue_add_indirect_packed(vq, sgs, total_sg,
-				out_sgs, in_sgs, data, gfp);
+	if (virtqueue_use_indirect(_vq, total_sg)) {
+		desc = alloc_indirect_packed(total_sg, gfp);
+		if (desc) {
+			return virtqueue_add_indirect_packed(vq, sgs, desc,
+							     total_sg,
+							     out_sgs, in_sgs,
+							     data, gfp);
+		}