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From:   Ursula Braun <ubraun@linux.ibm.com>
To:     davem@davemloft.net
Cc:     netdev@vger.kernel.org, linux-s390@vger.kernel.org,
        schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
        raspl@linux.ibm.com, linux-kernel@vger.kernel.org
Subject: [PATCH net 3/3] net/smc: move sock lock in smc_ioctl()
Date:   Wed,  8 Aug 2018 14:13:21 +0200
In-Reply-To: <20180808121321.516-1-ubraun@linux.ibm.com>
References: <20180808121321.516-1-ubraun@linux.ibm.com>
Message-Id: <20180808121321.516-4-ubraun@linux.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

When an SMC socket is connecting it is decided whether fallback to
TCP is needed. To avoid races between connect and ioctl move the
sock lock before the use_fallback check.

Reported-by: syzbot+5b2cece1a8ecb2ca77d8@syzkaller.appspotmail.com
Reported-by: syzbot+19557374321ca3710990@syzkaller.appspotmail.com
Fixes: 1992d99882af ("net/smc: take sock lock in smc_ioctl()")
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
---
 net/smc/af_smc.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 0ee7721afbe5..e7de5f282722 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1522,12 +1522,16 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
 
 	smc = smc_sk(sock->sk);
 	conn = &smc->conn;
+	lock_sock(&smc->sk);
 	if (smc->use_fallback) {
-		if (!smc->clcsock)
+		if (!smc->clcsock) {
+			release_sock(&smc->sk);
 			return -EBADF;
-		return smc->clcsock->ops->ioctl(smc->clcsock, cmd, arg);
+		}
+		answ = smc->clcsock->ops->ioctl(smc->clcsock, cmd, arg);
+		release_sock(&smc->sk);
+		return answ;
 	}
-	lock_sock(&smc->sk);
 	switch (cmd) {
 	case SIOCINQ: /* same as FIONREAD */
 		if (smc->sk.sk_state == SMC_LISTEN) {
-- 
2.16.4