[PATCH net] net/smc: avoid fallback in case of non-blocking connect

[Karsten Graul]

From: Ursula Braun <ubr...@linux.ibm.com>

FASTOPEN is not possible with SMC. sendmsg() with msg_flag MSG_FASTOPEN
triggers a fallback to TCP if the socket is in state SMC_INIT.
But if a nonblocking connect is already started, fallback to TCP
is no longer possible, even though the socket may still be in state
SMC_INIT.
And if a nonblocking connect is already started, a listen() call
does not make sense.

Reported-by: syzbot+bd8cc73d665590a1f...@syzkaller.appspotmail.com
Fixes: 50717a37db032 ("net/smc: nonblocking connect rework")
Signed-off-by: Ursula Braun <ubr...@linux.ibm.com>
Signed-off-by: Karsten Graul <kgr...@linux.ibm.com>
---
 net/smc/af_smc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index f5ea09258ab0..5b932583e407 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -263,7 +263,7 @@ static int smc_bind(struct socket *sock, struct sockaddr 
*uaddr,
 
        /* Check if socket is already active */
        rc = -EINVAL;
-       if (sk->sk_state != SMC_INIT)
+       if (sk->sk_state != SMC_INIT || smc->connect_nonblock)
                goto out_rel;
 
        smc->clcsock->sk->sk_reuse = sk->sk_reuse;
@@ -1390,7 +1390,8 @@ static int smc_listen(struct socket *sock, int backlog)
        lock_sock(sk);
 
        rc = -EINVAL;
-       if ((sk->sk_state != SMC_INIT) && (sk->sk_state != SMC_LISTEN))
+       if ((sk->sk_state != SMC_INIT && sk->sk_state != SMC_LISTEN) ||
+           smc->connect_nonblock)
                goto out;
 
        rc = 0;
@@ -1518,7 +1519,7 @@ static int smc_sendmsg(struct socket *sock, struct msghdr 
*msg, size_t len)
                goto out;
 
        if (msg->msg_flags & MSG_FASTOPEN) {
-               if (sk->sk_state == SMC_INIT) {
+               if (sk->sk_state == SMC_INIT && !smc->connect_nonblock) {
                        smc_switch_to_fallback(smc);
                        smc->fallback_rsn = SMC_CLC_DECL_OPTUNSUPP;
                } else {
-- 
2.21.0