[PATCH v4 2/2] virtio_ring: check desc == NULL when using indirect with packed

Xuan Zhuo
2021-10-19T11:52:35Z

When using indirect with packed, we don't check for allocation failures.
This patch checks that and fall back on direct.

Fixes: 1ce9e6055fa ("virtio_ring: introduce packed ring support")
Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 91a46c4da87d..44a03b6e4dc4 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1065,6 +1065,9 @@ static int virtqueue_add_indirect_packed(struct
vring_virtqueue *vq,

 	head = vq->packed.next_avail_idx;
 	desc = alloc_indirect_packed(total_sg, gfp);
+	if (!desc)
+		/* fall back on direct */
+		return -EAGAIN;

 	if (unlikely(vq->vq.num_free < 1)) {
 		pr_debug("Can't add buf len 1 - avail = 0\n");
@@ -1176,6 +1179,7 @@ static inline int virtqueue_add_packed(struct virtqueue
*_vq,
 	unsigned int i, n, c, descs_used, err_idx;
 	__le16 head_flags, flags;
 	u16 head, id, prev, curr, avail_used_flags;
+	int err;

 	START_USE(vq);

@@ -1191,9 +1195,12 @@ 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)) {
+		err = virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs,
+						    in_sgs, data, gfp);
+		if (err != -EAGAIN)
+			return err;
+	}

 	head = vq->packed.next_avail_idx;
 	avail_used_flags = vq->packed.avail_used_flags;
--
2.31.0