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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,
        eric.dumazet@gmail.com, lifeasageek@gmail.com, sbrivio@redhat.com
Subject: [PATCH net V2 1/1] net/smc: take sock lock in smc_ioctl()
Date:   Mon, 16 Jul 2018 13:56:52 +0200
Message-Id: <20180716115652.72331-1-ubraun@linux.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Ursula Braun <ursula.braun@linux.ibm.com>

SMC ioctl processing requires the sock lock to work properly in
all thinkable scenarios.
Problem has been found with RaceFuzzer and fixes:
   KASAN: null-ptr-deref Read in smc_ioctl

Reported-by: Byoungyoung Lee <lifeasageek@gmail.com>
Reported-by: syzbot+35b2c5aa76fd398b9fd4@syzkaller.appspotmail.com
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
---
 net/smc/af_smc.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 5334157f5065..c12a7fc18f56 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1524,10 +1524,13 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
 			return -EBADF;
 		return smc->clcsock->ops->ioctl(smc->clcsock, cmd, arg);
 	}
+	lock_sock(&smc->sk);
 	switch (cmd) {
 	case SIOCINQ: /* same as FIONREAD */
-		if (smc->sk.sk_state == SMC_LISTEN)
+		if (smc->sk.sk_state == SMC_LISTEN) {
+			release_sock(&smc->sk);
 			return -EINVAL;
+		}
 		if (smc->sk.sk_state == SMC_INIT ||
 		    smc->sk.sk_state == SMC_CLOSED)
 			answ = 0;
@@ -1536,8 +1539,10 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
 		break;
 	case SIOCOUTQ:
 		/* output queue size (not send + not acked) */
-		if (smc->sk.sk_state == SMC_LISTEN)
+		if (smc->sk.sk_state == SMC_LISTEN) {
+			release_sock(&smc->sk);
 			return -EINVAL;
+		}
 		if (smc->sk.sk_state == SMC_INIT ||
 		    smc->sk.sk_state == SMC_CLOSED)
 			answ = 0;
@@ -1547,8 +1552,10 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
 		break;
 	case SIOCOUTQNSD:
 		/* output queue size (not send only) */
-		if (smc->sk.sk_state == SMC_LISTEN)
+		if (smc->sk.sk_state == SMC_LISTEN) {
+			release_sock(&smc->sk);
 			return -EINVAL;
+		}
 		if (smc->sk.sk_state == SMC_INIT ||
 		    smc->sk.sk_state == SMC_CLOSED)
 			answ = 0;
@@ -1556,8 +1563,10 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
 			answ = smc_tx_prepared_sends(&smc->conn);
 		break;
 	case SIOCATMARK:
-		if (smc->sk.sk_state == SMC_LISTEN)
+		if (smc->sk.sk_state == SMC_LISTEN) {
+			release_sock(&smc->sk);
 			return -EINVAL;
+		}
 		if (smc->sk.sk_state == SMC_INIT ||
 		    smc->sk.sk_state == SMC_CLOSED) {
 			answ = 0;
@@ -1573,8 +1582,10 @@ static int smc_ioctl(struct socket *sock, unsigned int cmd,
 		}
 		break;
 	default:
+		release_sock(&smc->sk);
 		return -ENOIOCTLCMD;
 	}
+	release_sock(&smc->sk);
 
 	return put_user(answ, (int __user *)arg);
 }
-- 
2.16.4