Merge branch 'net-fix-uaf-of-sk_dst_get-sk-dev'

Kuniyuki Iwashima says:

====================
net: Fix UAF of sk_dst_get(sk)->dev.

syzbot caught use-after-free of sk_dst_get(sk)->dev,
which was not fetched under RCU nor RTNL. [0]

Patch 1 ~ 5, 7 fix UAF in smc, tcp, ktls, mptcp
Patch 6 fixes dst ref leak in mptcp

[0]: https://lore.kernel.org/[e-mail]

v1: https://lore.kernel.org/[e-mail]
====================

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/mptcp/ctrl.c

···
 	struct mptcp_pernet *pernet = mptcp_get_pernet(sock_net(sk));
 
 	if (atomic_read(&pernet->active_disable_times)) {
-		struct dst_entry *dst = sk_dst_get(sk);
+		struct net_device *dev;
+		struct dst_entry *dst;
 
-		if (dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK))
+		rcu_read_lock();
+		dst = __sk_dst_get(sk);
+		dev = dst ? dst_dev_rcu(dst) : NULL;
+		if (dev && (dev->flags & IFF_LOOPBACK))
 			atomic_set(&pernet->active_disable_times, 0);
+		rcu_read_unlock();
 	}
 }
 

net/smc/smc_clc.c

···
 }
 
 /* find ipv4 addr on device and get the prefix len, fill CLC proposal msg */
-static int smc_clc_prfx_set4_rcu(struct dst_entry *dst, __be32 ipv4,
+static int smc_clc_prfx_set4_rcu(struct net_device *dev, __be32 ipv4,
 				 struct smc_clc_msg_proposal_prefix *prop)
 {
-	struct in_device *in_dev = __in_dev_get_rcu(dst->dev);
+	struct in_device *in_dev = __in_dev_get_rcu(dev);
 	const struct in_ifaddr *ifa;
 
 	if (!in_dev)
···
 }
 
 /* fill CLC proposal msg with ipv6 prefixes from device */
-static int smc_clc_prfx_set6_rcu(struct dst_entry *dst,
+static int smc_clc_prfx_set6_rcu(struct net_device *dev,
 				 struct smc_clc_msg_proposal_prefix *prop,
 				 struct smc_clc_ipv6_prefix *ipv6_prfx)
 {
 #if IS_ENABLED(CONFIG_IPV6)
-	struct inet6_dev *in6_dev = __in6_dev_get(dst->dev);
+	struct inet6_dev *in6_dev = __in6_dev_get(dev);
 	struct inet6_ifaddr *ifa;
 	int cnt = 0;
 
···
 			    struct smc_clc_msg_proposal_prefix *prop,
 			    struct smc_clc_ipv6_prefix *ipv6_prfx)
 {
-	struct dst_entry *dst = sk_dst_get(clcsock->sk);
 	struct sockaddr_storage addrs;
 	struct sockaddr_in6 *addr6;
 	struct sockaddr_in *addr;
+	struct net_device *dev;
+	struct dst_entry *dst;
 	int rc = -ENOENT;
 
-	if (!dst) {
-		rc = -ENOTCONN;
-		goto out;
-	}
-	if (!dst->dev) {
-		rc = -ENODEV;
-		goto out_rel;
-	}
 	/* get address to which the internal TCP socket is bound */
 	if (kernel_getsockname(clcsock, (struct sockaddr *)&addrs) < 0)
-		goto out_rel;
+		goto out;
+
 	/* analyze IP specific data of net_device belonging to TCP socket */
 	addr6 = (struct sockaddr_in6 *)&addrs;
+
 	rcu_read_lock();
+
+	dst = __sk_dst_get(clcsock->sk);
+	dev = dst ? dst_dev_rcu(dst) : NULL;
+	if (!dev) {
+		rc = -ENODEV;
+		goto out_unlock;
+	}
+
 	if (addrs.ss_family == PF_INET) {
 		/* IPv4 */
 		addr = (struct sockaddr_in *)&addrs;
-		rc = smc_clc_prfx_set4_rcu(dst, addr->sin_addr.s_addr, prop);
+		rc = smc_clc_prfx_set4_rcu(dev, addr->sin_addr.s_addr, prop);
 	} else if (ipv6_addr_v4mapped(&addr6->sin6_addr)) {
 		/* mapped IPv4 address - peer is IPv4 only */
-		rc = smc_clc_prfx_set4_rcu(dst, addr6->sin6_addr.s6_addr32[3],
+		rc = smc_clc_prfx_set4_rcu(dev, addr6->sin6_addr.s6_addr32[3],
 					   prop);
 	} else {
 		/* IPv6 */
-		rc = smc_clc_prfx_set6_rcu(dst, prop, ipv6_prfx);
+		rc = smc_clc_prfx_set6_rcu(dev, prop, ipv6_prfx);
 	}
+
+out_unlock:
 	rcu_read_unlock();
-out_rel:
-	dst_release(dst);
 out:
 	return rc;
 }
···
 int smc_clc_prfx_match(struct socket *clcsock,
 		       struct smc_clc_msg_proposal_prefix *prop)
 {
-	struct dst_entry *dst = sk_dst_get(clcsock->sk);
+	struct net_device *dev;
+	struct dst_entry *dst;
 	int rc;
 
-	if (!dst) {
-		rc = -ENOTCONN;
+	rcu_read_lock();
+
+	dst = __sk_dst_get(clcsock->sk);
+	dev = dst ? dst_dev_rcu(dst) : NULL;
+	if (!dev) {
+		rc = -ENODEV;
 		goto out;
 	}
-	if (!dst->dev) {
-		rc = -ENODEV;
-		goto out_rel;
-	}
-	rcu_read_lock();
+
 	if (!prop->ipv6_prefixes_cnt)
-		rc = smc_clc_prfx_match4_rcu(dst->dev, prop);
+		rc = smc_clc_prfx_match4_rcu(dev, prop);
 	else
-		rc = smc_clc_prfx_match6_rcu(dst->dev, prop);
-	rcu_read_unlock();
-out_rel:
-	dst_release(dst);
+		rc = smc_clc_prfx_match6_rcu(dev, prop);
 out:
+	rcu_read_unlock();
+
 	return rc;
 }
 

net/smc/smc_core.c

···
 /* Determine vlan of internal TCP socket. */
 int smc_vlan_by_tcpsk(struct socket *clcsock, struct smc_init_info *ini)
 {
-	struct dst_entry *dst = sk_dst_get(clcsock->sk);
 	struct netdev_nested_priv priv;
 	struct net_device *ndev;
+	struct dst_entry *dst;
 	int rc = 0;
 
 	ini->vlan_id = 0;
-	if (!dst) {
-		rc = -ENOTCONN;
+
+	rcu_read_lock();
+
+	dst = __sk_dst_get(clcsock->sk);
+	ndev = dst ? dst_dev_rcu(dst) : NULL;
+	if (!ndev) {
+		rc = -ENODEV;
 		goto out;
 	}
-	if (!dst->dev) {
-		rc = -ENODEV;
-		goto out_rel;
-	}
 
-	ndev = dst->dev;
 	if (is_vlan_dev(ndev)) {
 		ini->vlan_id = vlan_dev_vlan_id(ndev);
-		goto out_rel;
+		goto out;
 	}
 
 	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);
+	netdev_walk_all_lower_dev_rcu(ndev, smc_vlan_by_tcpsk_walk, &priv);
 out:
+	rcu_read_unlock();
+
 	return rc;
 }
 

net/smc/smc_pnet.c

···
  */
 void smc_pnet_find_roce_resource(struct sock *sk, struct smc_init_info *ini)
 {
-	struct dst_entry *dst = sk_dst_get(sk);
+	struct net_device *dev;
+	struct dst_entry *dst;
 
-	if (!dst)
-		goto out;
-	if (!dst->dev)
-		goto out_rel;
+	rcu_read_lock();
+	dst = __sk_dst_get(sk);
+	dev = dst ? dst_dev_rcu(dst) : NULL;
+	dev_hold(dev);
+	rcu_read_unlock();
 
-	smc_pnet_find_roce_by_pnetid(dst->dev, ini);
-
-out_rel:
-	dst_release(dst);
-out:
-	return;
+	if (dev) {
+		smc_pnet_find_roce_by_pnetid(dev, ini);
+		dev_put(dev);
+	}
 }
 
 void smc_pnet_find_ism_resource(struct sock *sk, struct smc_init_info *ini)
 {
-	struct dst_entry *dst = sk_dst_get(sk);
+	struct net_device *dev;
+	struct dst_entry *dst;
 
 	ini->ism_dev[0] = NULL;
-	if (!dst)
-		goto out;
-	if (!dst->dev)
-		goto out_rel;
 
-	smc_pnet_find_ism_by_pnetid(dst->dev, ini);
+	rcu_read_lock();
+	dst = __sk_dst_get(sk);
+	dev = dst ? dst_dev_rcu(dst) : NULL;
+	dev_hold(dev);
+	rcu_read_unlock();
 
-out_rel:
-	dst_release(dst);
-out:
-	return;
+	if (dev) {
+		smc_pnet_find_ism_by_pnetid(dev, ini);
+		dev_put(dev);
+	}
 }
 
 /* Lookup and apply a pnet table entry to the given ib device.

net/tls/tls_device.c

···
 /* We assume that the socket is already connected */
 static struct net_device *get_netdev_for_sock(struct sock *sk)
 {
-	struct dst_entry *dst = sk_dst_get(sk);
-	struct net_device *netdev = NULL;
+	struct net_device *dev, *lowest_dev = NULL;
+	struct dst_entry *dst;
 
-	if (likely(dst)) {
-		netdev = netdev_sk_get_lowest_dev(dst->dev, sk);
-		dev_hold(netdev);
+	rcu_read_lock();
+	dst = __sk_dst_get(sk);
+	dev = dst ? dst_dev_rcu(dst) : NULL;
+	if (likely(dev)) {
+		lowest_dev = netdev_sk_get_lowest_dev(dev, sk);
+		dev_hold(lowest_dev);
 	}
+	rcu_read_unlock();
 
-	dst_release(dst);
-
-	return netdev;
+	return lowest_dev;
 }
 
 static void destroy_record(struct tls_record_info *record)