Merge branch 'dccp-tcp-fix-bhash2-issues-related-to-warn_on-in-inet_csk_get_port'

Kuniyuki Iwashima says:

====================
dccp/tcp: Fix bhash2 issues related to WARN_ON() in inet_csk_get_port().

syzkaller was hitting a WARN_ON() in inet_csk_get_port() in the 4th patch,
which was because we forgot to fix up bhash2 bucket when connect() for a
socket bound to a wildcard address fails in __inet_stream_connect().

There was a similar report [0], but its repro does not fire the WARN_ON() due
to inconsistent error handling.

When connect() for a socket bound to a wildcard address fails, saddr may or
may not be reset depending on where the failure happens.  When we fail in
__inet_stream_connect(), sk->sk_prot->disconnect() resets saddr.  OTOH, in
(dccp|tcp)_v[46]_connect(), if we fail after inet_hash6?_connect(), we
forget to reset saddr.

We fix this inconsistent error handling in the 1st patch, and then we'll
fix the bhash2 WARN_ON() issue.

Note that there is still an issue in that we reset saddr without checking
if there are conflicting sockets in bhash and bhash2, but this should be
another series.

See [1][2] for the previous discussion.

[0]: https://lore.kernel.org/netdev/0000000000003f33bc05dfaf44fe@google.com/
[1]: https://lore.kernel.org/netdev/20221029001249.86337-1-kuniyu@amazon.com/
[2]: https://lore.kernel.org/netdev/20221103172419.20977-1-kuniyu@amazon.com/
[3]: https://lore.kernel.org/netdev/20221118081906.053d5231@kernel.org/T/#m00aafedb29ff0b55d5e67aef0252ef1baaf4b6ee
====================

Link: https://lore.kernel.org/r/20221119014914.31792-1-kuniyu@amazon.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/inet_hashtables.h

@@ -281,7 +281,8 @@ inet_bhash2_addr_any_hashbucket(const struct sock *sk, const struct net *net, in
  * sk_v6_rcv_saddr (ipv6) changes after it has been binded. The socket's
  * rcv_saddr field should already have been updated when this is called.
  */
-int inet_bhash2_update_saddr(struct inet_bind_hashbucket *prev_saddr, struct sock *sk);
+int inet_bhash2_update_saddr(struct sock *sk, void *saddr, int family);
+void inet_bhash2_reset_saddr(struct sock *sk);
 
 void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
 		    struct inet_bind2_bucket *tb2, unsigned short port);

net/dccp/ipv4.c

@@ -45,11 +45,10 @@ static unsigned int dccp_v4_pernet_id __read_mostly;
 int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 {
 	const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
-	struct inet_bind_hashbucket *prev_addr_hashbucket = NULL;
-	__be32 daddr, nexthop, prev_sk_rcv_saddr;
 	struct inet_sock *inet = inet_sk(sk);
 	struct dccp_sock *dp = dccp_sk(sk);
 	__be16 orig_sport, orig_dport;
+	__be32 daddr, nexthop;
 	struct flowi4 *fl4;
 	struct rtable *rt;
 	int err;
@@ -91,26 +90,13 @@ int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 		daddr = fl4->daddr;
 
 	if (inet->inet_saddr == 0) {
-		if (inet_csk(sk)->icsk_bind2_hash) {
-			prev_addr_hashbucket =
-				inet_bhashfn_portaddr(&dccp_hashinfo, sk,
-						      sock_net(sk),
-						      inet->inet_num);
-			prev_sk_rcv_saddr = sk->sk_rcv_saddr;
-		}
-		inet->inet_saddr = fl4->saddr;
-	}
-
-	sk_rcv_saddr_set(sk, inet->inet_saddr);
-
-	if (prev_addr_hashbucket) {
-		err = inet_bhash2_update_saddr(prev_addr_hashbucket, sk);
+		err = inet_bhash2_update_saddr(sk,  &fl4->saddr, AF_INET);
 		if (err) {
-			inet->inet_saddr = 0;
-			sk_rcv_saddr_set(sk, prev_sk_rcv_saddr);
 			ip_rt_put(rt);
 			return err;
 		}
+	} else {
+		sk_rcv_saddr_set(sk, inet->inet_saddr);
 	}
 
 	inet->inet_dport = usin->sin_port;
@@ -157,6 +143,7 @@ int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	 * This unhashes the socket and releases the local port, if necessary.
 	 */
 	dccp_set_state(sk, DCCP_CLOSED);
+	inet_bhash2_reset_saddr(sk);
 	ip_rt_put(rt);
 	sk->sk_route_caps = 0;
 	inet->inet_dport = 0;

net/dccp/ipv6.c

@@ -934,26 +934,11 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	}
 
 	if (saddr == NULL) {
-		struct inet_bind_hashbucket *prev_addr_hashbucket = NULL;
-		struct in6_addr prev_v6_rcv_saddr;
-
-		if (icsk->icsk_bind2_hash) {
-			prev_addr_hashbucket = inet_bhashfn_portaddr(&dccp_hashinfo,
-								     sk, sock_net(sk),
-								     inet->inet_num);
-			prev_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
-		}
-
 		saddr = &fl6.saddr;
-		sk->sk_v6_rcv_saddr = *saddr;
-
-		if (prev_addr_hashbucket) {
-			err = inet_bhash2_update_saddr(prev_addr_hashbucket, sk);
-			if (err) {
-				sk->sk_v6_rcv_saddr = prev_v6_rcv_saddr;
-				goto failure;
-			}
-		}
+
+		err = inet_bhash2_update_saddr(sk, saddr, AF_INET6);
+		if (err)
+			goto failure;
 	}
 
 	/* set the source address */
@@ -985,6 +970,7 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 
 late_failure:
 	dccp_set_state(sk, DCCP_CLOSED);
+	inet_bhash2_reset_saddr(sk);
 	__sk_dst_reset(sk);
 failure:
 	inet->inet_dport = 0;

net/dccp/proto.c

@@ -279,8 +279,7 @@ int dccp_disconnect(struct sock *sk, int flags)
 
 	inet->inet_dport = 0;
 
-	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
-		inet_reset_saddr(sk);
+	inet_bhash2_reset_saddr(sk);
 
 	sk->sk_shutdown = 0;
 	sock_reset_flag(sk, SOCK_DONE);

net/ipv4/af_inet.c

@@ -1230,7 +1230,6 @@ EXPORT_SYMBOL(inet_unregister_protosw);
 
 static int inet_sk_reselect_saddr(struct sock *sk)
 {
-	struct inet_bind_hashbucket *prev_addr_hashbucket;
 	struct inet_sock *inet = inet_sk(sk);
 	__be32 old_saddr = inet->inet_saddr;
 	__be32 daddr = inet->inet_daddr;
@@ -1260,16 +1259,8 @@ static int inet_sk_reselect_saddr(struct sock *sk)
 		return 0;
 	}
 
-	prev_addr_hashbucket =
-		inet_bhashfn_portaddr(tcp_or_dccp_get_hashinfo(sk), sk,
-				      sock_net(sk), inet->inet_num);
-
-	inet->inet_saddr = inet->inet_rcv_saddr = new_saddr;
-
-	err = inet_bhash2_update_saddr(prev_addr_hashbucket, sk);
+	err = inet_bhash2_update_saddr(sk, &new_saddr, AF_INET);
 	if (err) {
-		inet->inet_saddr = old_saddr;
-		inet->inet_rcv_saddr = old_saddr;
 		ip_rt_put(rt);
 		return err;
 	}

net/ipv4/inet_hashtables.c

@@ -858,34 +858,80 @@ inet_bhash2_addr_any_hashbucket(const struct sock *sk, const struct net *net, in
 	return &hinfo->bhash2[hash & (hinfo->bhash_size - 1)];
 }
 
-int inet_bhash2_update_saddr(struct inet_bind_hashbucket *prev_saddr, struct sock *sk)
+static void inet_update_saddr(struct sock *sk, void *saddr, int family)
+{
+	if (family == AF_INET) {
+		inet_sk(sk)->inet_saddr = *(__be32 *)saddr;
+		sk_rcv_saddr_set(sk, inet_sk(sk)->inet_saddr);
+	}
+#if IS_ENABLED(CONFIG_IPV6)
+	else {
+		sk->sk_v6_rcv_saddr = *(struct in6_addr *)saddr;
+	}
+#endif
+}
+
+static int __inet_bhash2_update_saddr(struct sock *sk, void *saddr, int family, bool reset)
 {
 	struct inet_hashinfo *hinfo = tcp_or_dccp_get_hashinfo(sk);
+	struct inet_bind_hashbucket *head, *head2;
 	struct inet_bind2_bucket *tb2, *new_tb2;
 	int l3mdev = inet_sk_bound_l3mdev(sk);
-	struct inet_bind_hashbucket *head2;
 	int port = inet_sk(sk)->inet_num;
 	struct net *net = sock_net(sk);
+	int bhash;
+
+	if (!inet_csk(sk)->icsk_bind2_hash) {
+		/* Not bind()ed before. */
+		if (reset)
+			inet_reset_saddr(sk);
+		else
+			inet_update_saddr(sk, saddr, family);
+
+		return 0;
+	}
 
 	/* Allocate a bind2 bucket ahead of time to avoid permanently putting
 	 * the bhash2 table in an inconsistent state if a new tb2 bucket
 	 * allocation fails.
 	 */
 	new_tb2 = kmem_cache_alloc(hinfo->bind2_bucket_cachep, GFP_ATOMIC);
-	if (!new_tb2)
+	if (!new_tb2) {
+		if (reset) {
+			/* The (INADDR_ANY, port) bucket might have already
+			 * been freed, then we cannot fixup icsk_bind2_hash,
+			 * so we give up and unlink sk from bhash/bhash2 not
+			 * to leave inconsistency in bhash2.
+			 */
+			inet_put_port(sk);
+			inet_reset_saddr(sk);
+		}
+
 		return -ENOMEM;
+	}
 
+	bhash = inet_bhashfn(net, port, hinfo->bhash_size);
+	head = &hinfo->bhash[bhash];
 	head2 = inet_bhashfn_portaddr(hinfo, sk, net, port);
 
-	if (prev_saddr) {
-		spin_lock_bh(&prev_saddr->lock);
-		__sk_del_bind2_node(sk);
-		inet_bind2_bucket_destroy(hinfo->bind2_bucket_cachep,
-					  inet_csk(sk)->icsk_bind2_hash);
-		spin_unlock_bh(&prev_saddr->lock);
-	}
+	/* If we change saddr locklessly, another thread
+	 * iterating over bhash might see corrupted address.
+	 */
+	spin_lock_bh(&head->lock);
 
-	spin_lock_bh(&head2->lock);
+	spin_lock(&head2->lock);
+	__sk_del_bind2_node(sk);
+	inet_bind2_bucket_destroy(hinfo->bind2_bucket_cachep, inet_csk(sk)->icsk_bind2_hash);
+	spin_unlock(&head2->lock);
+
+	if (reset)
+		inet_reset_saddr(sk);
+	else
+		inet_update_saddr(sk, saddr, family);
+
+	head2 = inet_bhashfn_portaddr(hinfo, sk, net, port);
+
+	spin_lock(&head2->lock);
 	tb2 = inet_bind2_bucket_find(head2, net, port, l3mdev, sk);
 	if (!tb2) {
 		tb2 = new_tb2;
@@ -893,15 +939,29 @@ int inet_bhash2_update_saddr(struct inet_bind_hashbucket *prev_saddr, struct soc
 	}
 	sk_add_bind2_node(sk, &tb2->owners);
 	inet_csk(sk)->icsk_bind2_hash = tb2;
-	spin_unlock_bh(&head2->lock);
+	spin_unlock(&head2->lock);
+
+	spin_unlock_bh(&head->lock);
 
 	if (tb2 != new_tb2)
 		kmem_cache_free(hinfo->bind2_bucket_cachep, new_tb2);
 
 	return 0;
 }
+
+int inet_bhash2_update_saddr(struct sock *sk, void *saddr, int family)
+{
+	return __inet_bhash2_update_saddr(sk, saddr, family, false);
+}
 EXPORT_SYMBOL_GPL(inet_bhash2_update_saddr);
 
+void inet_bhash2_reset_saddr(struct sock *sk)
+{
+	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
+		__inet_bhash2_update_saddr(sk, NULL, 0, true);
+}
+EXPORT_SYMBOL_GPL(inet_bhash2_reset_saddr);
+
 /* RFC 6056 3.3.4.  Algorithm 4: Double-Hash Port Selection Algorithm
  * Note that we use 32bit integers (vs RFC 'short integers')
  * because 2^16 is not a multiple of num_ephemeral and this

net/ipv4/tcp.c

@@ -3114,8 +3114,7 @@ int tcp_disconnect(struct sock *sk, int flags)
 
 	inet->inet_dport = 0;
 
-	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
-		inet_reset_saddr(sk);
+	inet_bhash2_reset_saddr(sk);
 
 	sk->sk_shutdown = 0;
 	sock_reset_flag(sk, SOCK_DONE);

net/ipv4/tcp_ipv4.c

@@ -199,15 +199,14 @@ static int tcp_v4_pre_connect(struct sock *sk, struct sockaddr *uaddr,
 /* This will initiate an outgoing connection. */
 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 {
-	struct inet_bind_hashbucket *prev_addr_hashbucket = NULL;
 	struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
 	struct inet_timewait_death_row *tcp_death_row;
-	__be32 daddr, nexthop, prev_sk_rcv_saddr;
 	struct inet_sock *inet = inet_sk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct ip_options_rcu *inet_opt;
 	struct net *net = sock_net(sk);
 	__be16 orig_sport, orig_dport;
+	__be32 daddr, nexthop;
 	struct flowi4 *fl4;
 	struct rtable *rt;
 	int err;
@@ -251,24 +250,13 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
 
 	if (!inet->inet_saddr) {
-		if (inet_csk(sk)->icsk_bind2_hash) {
-			prev_addr_hashbucket = inet_bhashfn_portaddr(tcp_death_row->hashinfo,
-								     sk, net, inet->inet_num);
-			prev_sk_rcv_saddr = sk->sk_rcv_saddr;
-		}
-		inet->inet_saddr = fl4->saddr;
-	}
-
-	sk_rcv_saddr_set(sk, inet->inet_saddr);
-
-	if (prev_addr_hashbucket) {
-		err = inet_bhash2_update_saddr(prev_addr_hashbucket, sk);
+		err = inet_bhash2_update_saddr(sk,  &fl4->saddr, AF_INET);
 		if (err) {
-			inet->inet_saddr = 0;
-			sk_rcv_saddr_set(sk, prev_sk_rcv_saddr);
 			ip_rt_put(rt);
 			return err;
 		}
+	} else {
+		sk_rcv_saddr_set(sk, inet->inet_saddr);
 	}
 
 	if (tp->rx_opt.ts_recent_stamp && inet->inet_daddr != daddr) {
@@ -343,6 +331,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	 * if necessary.
 	 */
 	tcp_set_state(sk, TCP_CLOSE);
+	inet_bhash2_reset_saddr(sk);
 	ip_rt_put(rt);
 	sk->sk_route_caps = 0;
 	inet->inet_dport = 0;

net/ipv6/tcp_ipv6.c

@@ -292,24 +292,11 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
 
 	if (!saddr) {
-		struct inet_bind_hashbucket *prev_addr_hashbucket = NULL;
-		struct in6_addr prev_v6_rcv_saddr;
-
-		if (icsk->icsk_bind2_hash) {
-			prev_addr_hashbucket = inet_bhashfn_portaddr(tcp_death_row->hashinfo,
-								     sk, net, inet->inet_num);
-			prev_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
-		}
 		saddr = &fl6.saddr;
-		sk->sk_v6_rcv_saddr = *saddr;
 
-		if (prev_addr_hashbucket) {
-			err = inet_bhash2_update_saddr(prev_addr_hashbucket, sk);
-			if (err) {
-				sk->sk_v6_rcv_saddr = prev_v6_rcv_saddr;
-				goto failure;
-			}
-		}
+		err = inet_bhash2_update_saddr(sk, saddr, AF_INET6);
+		if (err)
+			goto failure;
 	}
 
 	/* set the source address */
@@ -359,6 +346,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 
 late_failure:
 	tcp_set_state(sk, TCP_CLOSE);
+	inet_bhash2_reset_saddr(sk);
 failure:
 	inet->inet_dport = 0;
 	sk->sk_route_caps = 0;