[dpdk-dev] [PATCH] vhost: fix corner case for split ring enqueue operation

[Gavin Hu (Arm Technology China)]

This is a good catch for split vring, I advise to change also for packed vring. It also has this issue.

> -----Original Message-----
> From: dev <dev-bounces at dpdk.org> On Behalf Of Jiayu Hu
> Sent: Friday, September 7, 2018 3:25 PM
> To: dev at dpdk.org
> Cc: zhihong.wang at intel.com; tiwei.bie at intel.com;
> maxime.coquelin at redhat.com; Jiayu Hu <jiayu.hu at intel.com>
> Subject: [dpdk-dev] [PATCH] vhost: fix corner case for split ring enqueue
> operation
>
> When perform enqueue operations on the split ring, if the reserved buffer
> length from the descriptor table execeeds 65535, the returned length by
> fill_vec_buf_split() is overflowed.
> This patch is to avoid this corner case.
>
> Fixes: f689586bc060 ("vhost: shadow used ring update")
>
> Signed-off-by: Jiayu Hu <jiayu.hu at intel.com>
> ---
>  lib/librte_vhost/virtio_net.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c index
> 99c7afc..9f3c88f 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -122,7 +122,7 @@ flush_shadow_used_ring_split(struct virtio_net *dev,
> struct vhost_virtqueue *vq)
>
>  static __rte_always_inline void
>  update_shadow_used_ring_split(struct vhost_virtqueue *vq,
> - uint16_t desc_idx, uint16_t len)
> + uint16_t desc_idx, uint32_t len)
>  {
>  uint16_t i = vq->shadow_used_idx++;
>
> @@ -329,7 +329,7 @@ static __rte_always_inline int  fill_vec_buf_split(struct
> virtio_net *dev, struct vhost_virtqueue *vq,
>   uint32_t avail_idx, uint16_t *vec_idx,
>   struct buf_vector *buf_vec, uint16_t
> *desc_chain_head,
> - uint16_t *desc_chain_len, uint8_t perm)
> + uint32_t *desc_chain_len, uint8_t perm)
>  {
>  uint16_t idx = vq->avail->ring[avail_idx & (vq->size - 1)];
>  uint16_t vec_id = *vec_idx;
> @@ -409,7 +409,7 @@ reserve_avail_buf_split(struct virtio_net *dev, struct
> vhost_virtqueue *vq,
>  uint16_t max_tries, tries = 0;
>
>  uint16_t head_idx = 0;
> -uint16_t len = 0;
> +uint32_t len = 0;
>
>  *num_buffers = 0;
>  cur_idx  = vq->last_avail_idx;
> @@ -1378,7 +1378,8 @@ virtio_dev_tx_split(struct virtio_net *dev, struct
> vhost_virtqueue *vq,
>
>  for (i = 0; i < count; i++) {
>  struct buf_vector buf_vec[BUF_VECTOR_MAX];
> -uint16_t head_idx, dummy_len;
> +uint16_t head_idx;
> +uint32_t dummy_len;
>  uint16_t nr_vec = 0;
>  int err;
>
> --
> 2.7.4

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