[PATCH 4.16 15/55] net/smc: restrict non-blocking connect finish

Greg Kroah-Hartman
2018-05-18T08:15:11Z

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

[ Upstream commit 784813aed6ba24a1f24e7e11d9d0f208cee37a7d ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/smc/af_smc.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1165,13 +1165,15 @@ static __poll_t smc_poll(struct file *fi
/* 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;