[PATCH 4.20 021/117] tcp: allow MSG_ZEROCOPY transmission also in CLOSE_WAIT state

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Willem de Bruijn <willemb@xxxxxxxxxx>

[ Upstream commit 13d7f46386e060df31b727c9975e38306fa51e7a ]

TCP transmission with MSG_ZEROCOPY fails if the peer closes its end of
the connection and so transitions this socket to CLOSE_WAIT state.

Transmission in close wait state is acceptable. Other similar tests in
the stack (e.g., in FastOpen) accept both states. Relax this test, too.

Link: https://www.mail-archive.com/netdev@xxxxxxxxxxxxxxx/msg276886.html
Link: https://www.mail-archive.com/netdev@xxxxxxxxxxxxxxx/msg227390.html
Fixes: f214f915e7db ("tcp: enable MSG_ZEROCOPY")
Reported-by: Marek Majkowski <marek@xxxxxxxxxxxxxx>
Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
CC: Yuchung Cheng <ycheng@xxxxxxxxxx>
CC: Neal Cardwell <ncardwell@xxxxxxxxxx>
CC: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
CC: Alexey Kodanev <alexey.kodanev@xxxxxxxxxx>
Acked-by: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv4/tcp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1186,7 +1186,7 @@ int tcp_sendmsg_locked(struct sock *sk,
 	flags = msg->msg_flags;
 
 	if (flags & MSG_ZEROCOPY && size && sock_flag(sk, SOCK_ZEROCOPY)) {
-		if (sk->sk_state != TCP_ESTABLISHED) {
+		if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
 			err = -EINVAL;
 			goto out_err;
 		}