[PATCH net 1/1] net/smc: fix refcounting for non-blocking connect()

If a nonblocking socket is immediately closed after connect(),
the connect worker may not have started. This results in a refcount
problem, since sock_hold() is called from the connect worker.
This patch moves the sock_hold in front of the connect worker
scheduling.

Reported-by: syzbot+4c063e6dea39e4b79f29@syzkaller.appspotmail.com
Fixes: 50717a37db03 ("net/smc: nonblocking connect rework")
Reviewed-by: Karsten Graul <redacted>
Signed-off-by: Ursula Braun <redacted>
---
 net/smc/af_smc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index cea3c36ea0da..47946f489fd4 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c

@@ -707,8 +707,6 @@ static int __smc_connect(struct smc_sock *smc)
 	int smc_type;
 	int rc = 0;
 
-	sock_hold(&smc->sk); /* sock put in passive closing */
-
 	if (smc->use_fallback)
 		return smc_connect_fallback(smc, smc->fallback_rsn);
 

@@ -853,6 +851,8 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr,
 	rc = kernel_connect(smc->clcsock, addr, alen, flags);
 	if (rc && rc != -EINPROGRESS)
 		goto out;
+
+	sock_hold(&smc->sk); /* sock put in passive closing */
 	if (flags & O_NONBLOCK) {
 		if (schedule_work(&smc->connect_work))
 			smc->connect_nonblock = 1;

-- 
2.17.1

From: Ursula Braun <redacted>
Date: Tue, 29 Oct 2019 12:41:26 +0100

If a nonblocking socket is immediately closed after connect(),
the connect worker may not have started. This results in a refcount
problem, since sock_hold() is called from the connect worker.
This patch moves the sock_hold in front of the connect worker
scheduling.

Reported-by: syzbot+4c063e6dea39e4b79f29@syzkaller.appspotmail.com
Fixes: 50717a37db03 ("net/smc: nonblocking connect rework")
Reviewed-by: Karsten Graul <redacted>
Signed-off-by: Ursula Braun <redacted>

Applied and queued up for -stable, thank you.