[PATCH net 1/4] net/smc: take sock lock in smc_ioctl()

[Ursula Braun <ubraun@linux.ibm.com>]

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 | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 5334157f5065..a4381b38a521 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1524,6 +1524,7 @@ 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)
@@ -1573,8 +1574,10 @@ 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