net/smc: restrict non-blocking connect finish

The smc_poll code tries to finish connect() if the socket is in
state SMC_INIT and polling of the internal CLC-socket returns with
EPOLLOUT. This makes sense for a select/poll call following a connect
call, but not without preceding connect().
With this patch smc_poll starts connect logic only, if the CLC-socket
is no longer in its initial state TCP_CLOSE.

In addition, a poll error on the internal CLC-socket is always
propagated to the SMC socket.

With this patch the code path mentioned by syzbot
https://syzkaller.appspot.com/bug?extid=03faa2dc16b8b64be396
is no longer possible.

Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Reported-by: syzbot+03faa2dc16b8b64be396@syzkaller.appspotmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 4470501374bf9882209ced0e065927e48e4cb857..8b4c059bd13b4b9f94dd811a525fe05274149cc9 100644 (file)
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1166,13 +1166,15 @@ static __poll_t smc_poll(struct file *file, struct socket *sock,
                /* delegate to CLC child sock */
                release_sock(sk);
                mask = smc->clcsock->ops->poll(file, smc->clcsock, wait);
-               /* if non-blocking connect finished ... */
                lock_sock(sk);
-               if ((sk->sk_state == SMC_INIT) && (mask & EPOLLOUT)) {
-                       sk->sk_err = smc->clcsock->sk->sk_err;
-                       if (sk->sk_err) {
-                               mask |= EPOLLERR;
-                       } else {
+               sk->sk_err = smc->clcsock->sk->sk_err;
+               if (sk->sk_err) {
+                       mask |= EPOLLERR;
+               } else {
+                       /* if non-blocking connect finished ... */
+                       if (sk->sk_state == SMC_INIT &&
+                           mask & EPOLLOUT &&
+                           smc->clcsock->sk->sk_state != TCP_CLOSE) {
                                rc = smc_connect_rdma(smc);
                                if (rc < 0)
                                        mask |= EPOLLERR;