tun: handle ubuf refcount correctly when meet errors (af1cc7a2) · Commits · 戴 / test

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 <wangyunjian@huawei.com> Signed-off-by:

Jason Wang <jasowang@redhat.com> Acked-by:

Michael S. Tsirkin <mst@redhat.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/net/tun.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -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);

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