On Wed, Nov 30, 2016 at 01:17:51PM +0800, Jason Wang wrote:
> We trigger uarg->callback() immediately after we decide do datacopy
> even if caller want to do zerocopy. This will cause the callback
> (vhost_net_zerocopy_callback) decrease the refcount. But when we meet
> an error afterwards, the error handling in vhost handle_tx() will try
> to decrease it again. This is wrong and fix this by delay the
> uarg->callback() until we're sure there's no errors.
>
> Reported-by: wangyunjian <wangyunj...@huawei.com>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> The patch is needed for -stable.
> ---
> drivers/net/tun.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 8093e39..db6acec 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1246,13 +1246,8 @@ static ssize_t tun_get_user(struct tun_struct *tun,
> struct tun_file *tfile,
>
> if (zerocopy)
> err = zerocopy_sg_from_iter(skb, from);
> - else {
> + else
> err = skb_copy_datagram_from_iter(skb, 0, from, len);
> - if (!err && msg_control) {
> - struct ubuf_info *uarg = msg_control;
> - uarg->callback(uarg, false);
> - }
> - }
>
> if (err) {
> this_cpu_inc(tun->pcpu_stats->rx_dropped);
> @@ -1298,6 +1293,9 @@ static ssize_t tun_get_user(struct tun_struct *tun,
> struct tun_file *tfile,
> skb_shinfo(skb)->destructor_arg = msg_control;
> skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
> skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
> + } else if (msg_control) {
> + struct ubuf_info *uarg = msg_control;
> + uarg->callback(uarg, false);
> }
>
> skb_reset_network_header(skb);
> --
> 2.7.4
