[PATCH 5.3 114/140] net/smc: fix refcounting for non-blocking connect()

[Greg Kroah-Hartman]

From: Ursula Braun <ubraun@xxxxxxxxxxxxx>

[ Upstream commit 301428ea3708188dc4a243e6e6b46c03b46a0fbc ]

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@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 50717a37db03 ("net/smc: nonblocking connect rework")
Reviewed-by: Karsten Graul <kgraul@xxxxxxxxxxxxx>
Signed-off-by: Ursula Braun <ubraun@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/smc/af_smc.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -707,8 +707,6 @@ static int __smc_connect(struct smc_sock
 	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 *so
 	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;