Re: [syzbot] [net?] possible deadlock in do_ipv6_setsockopt (4)

[Hillf Danton]

On Sun, 02 Feb 2025 14:01:18 -0800
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    c2933b2befe2 Merge tag 'net-6.14-rc1' of git://git.kernel...
> git tree:       net-next
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12c69724580000

#syz test

--- x/net/smc/af_smc.c
+++ y/net/smc/af_smc.c
@@ -1597,6 +1597,7 @@ static void smc_connect_work(struct work
 			rc = 0;
 	}
 	release_sock(smc->clcsock->sk);
+	rtnl_lock();
 	lock_sock(&smc->sk);
 	if (rc != 0 || smc->sk.sk_err) {
 		smc->sk.sk_state = SMC_CLOSED;
@@ -1624,6 +1625,7 @@ out:
 		}
 	}
 	release_sock(&smc->sk);
+	rtnl_unlock();
 }
 
 int smc_connect(struct socket *sock, struct sockaddr *addr,
@@ -1641,6 +1643,7 @@ int smc_connect(struct socket *sock, str
 	if (addr->sa_family != AF_INET && addr->sa_family != AF_INET6)
 		goto out_err;
 
+	rtnl_lock();
 	lock_sock(sk);
 	switch (sock->state) {
 	default:
@@ -1703,6 +1706,7 @@ connected:
 	sock->state = SS_CONNECTED;
 out:
 	release_sock(sk);
+	rtnl_unlock();
 out_err:
 	return rc;
 }
--- x/net/smc/smc_core.c
+++ y/net/smc/smc_core.c
@@ -1888,6 +1888,7 @@ int smc_vlan_by_tcpsk(struct socket *clc
 	struct net_device *ndev;
 	int rc = 0;
 
+	ASSERT_RTNL();
 	ini->vlan_id = 0;
 	if (!dst) {
 		rc = -ENOTCONN;
@@ -1905,9 +1906,7 @@ int smc_vlan_by_tcpsk(struct socket *clc
 	}
 
 	priv.data = (void *)&ini->vlan_id;
-	rtnl_lock();
 	netdev_walk_all_lower_dev(ndev, smc_vlan_by_tcpsk_walk, &priv);
-	rtnl_unlock();
 
 out_rel:
 	dst_release(dst);
--