* Re: [PATCH net v5 1/2] vhost_net: fix ubuf refcount incorrectly when sendmsg fails
[not found] <1608881065-7572-1-git-send-email-wangyunjian@huawei.com>
@ 2020-12-27 11:23 ` Michael S. Tsirkin
2020-12-27 16:14 ` Willem de Bruijn
0 siblings, 1 reply; 2+ messages in thread
From: Michael S. Tsirkin @ 2020-12-27 11:23 UTC (permalink / raw)
To: wangyunjian
Cc: willemdebruijn.kernel, netdev, jerry.lilijun, virtualization,
xudingke, brian.huangbin, chenchanghu
On Fri, Dec 25, 2020 at 03:24:25PM +0800, wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@huawei.com>
>
> Currently the vhost_zerocopy_callback() maybe be called to decrease
> the refcount when sendmsg fails in tun. The error handling in vhost
> handle_tx_zerocopy() will try to decrease the same refcount again.
> This is wrong. To fix this issue, we only call vhost_net_ubuf_put()
> when vq->heads[nvq->desc].len == VHOST_DMA_IN_PROGRESS.
>
> Fixes: 0690899b4d45 ("tun: experimental zero copy tx support")
Are you sure about this tag? the patch in question only affects
tun, while the fix only affects vhost.
> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
> Acked-by: Willem de Bruijn <willemb@google.com>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
> Acked-by: Jason Wang <jasowang@redhat.com>
> ---
> drivers/vhost/net.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 531a00d703cd..c8784dfafdd7 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -863,6 +863,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
> size_t len, total_len = 0;
> int err;
> struct vhost_net_ubuf_ref *ubufs;
> + struct ubuf_info *ubuf;
> bool zcopy_used;
> int sent_pkts = 0;
>
> @@ -895,9 +896,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
>
> /* use msg_control to pass vhost zerocopy ubuf info to skb */
> if (zcopy_used) {
> - struct ubuf_info *ubuf;
> ubuf = nvq->ubuf_info + nvq->upend_idx;
> -
> vq->heads[nvq->upend_idx].id = cpu_to_vhost32(vq, head);
> vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
> ubuf->callback = vhost_zerocopy_callback;
> @@ -927,7 +926,8 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
> err = sock->ops->sendmsg(sock, &msg, len);
> if (unlikely(err < 0)) {
> if (zcopy_used) {
> - vhost_net_ubuf_put(ubufs);
> + if (vq->heads[ubuf->desc].len == VHOST_DMA_IN_PROGRESS)
> + vhost_net_ubuf_put(ubufs);
> nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
> % UIO_MAXIOV;
> }
> --
> 2.23.0
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