netdev - [PATCH v1 net] dccp/tcp: Reset saddr on failure after inet6?_hash

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Date:   Thu, 3 Nov 2022 10:24:19 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>
CC:     Arnaldo Carvalho de Melo <acme@...driva.com>,
        Joanne Koong <joannelkoong@...il.com>,
        Martin KaFai Lau <martin.lau@...nel.org>,
        "Ziyang Xuan (William)" <william.xuanziyang@...wei.com>,
        Kuniyuki Iwashima <kuniyu@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        <netdev@...r.kernel.org>, <dccp@...r.kernel.org>
Subject: [PATCH v1 net] dccp/tcp: Reset saddr on failure after inet6?_hash_connect().

When connect() is called on a socket bound to the wildcard address,
we change the socket's saddr to a local address.  If the socket
fails to connect() to the destination, we have to reset the saddr.

However, when an error occurs after inet_hash6?_connect() in
(dccp|tcp)_v[46]_conect(), we forget to reset saddr and leave
the socket bound to the address.

>From the user's point of view, whether saddr is reset or not varies
with errno.  Let's fix this inconsistent behaviour.

Note that with this patch, the repro [0] will trigger the WARN_ON()
in inet_csk_get_port() again, but this patch is not buggy and rather
fixes a bug papering over the bhash2's bug [1] for which we need
another fix.

For the record, the repro causes -EADDRNOTAVAIL in inet_hash6_connect()
by this sequence:

  s1 = socket()
  s1.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
  s1.bind(('127.0.0.1', 10000))
  s1.sendto(b'hello', MSG_FASTOPEN, (('127.0.0.1', 10000)))
  # or s1.connect(('127.0.0.1', 10000))

  s2 = socket()
  s2.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
  s2.bind(('0.0.0.0', 10000))
  s2.connect(('127.0.0.1', 10000))  # -EADDRNOTAVAIL

  s2.listen(32)  # WARN_ON(inet_csk(sk)->icsk_bind2_hash != tb2);

[0]: https://syzkaller.appspot.com/bug?extid=015d756bbd1f8b5c8f09
[1]: https://lore.kernel.org/netdev/20221029001249.86337-1-kuniyu@amazon.com/

Fixes: 3df80d9320bc ("[DCCP]: Introduce DCCPv6")
Fixes: 7c657876b63c ("[DCCP]: Initial implementation")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/dccp/ipv4.c     | 2 ++
 net/dccp/ipv6.c     | 2 ++
 net/ipv4/tcp_ipv4.c | 2 ++
 net/ipv6/tcp_ipv6.c | 2 ++
 4 files changed, 8 insertions(+)

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 713b7b8dad7e..40640c26680e 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -157,6 +157,8 @@ 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);
+	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
+		inet_reset_saddr(sk);
 	ip_rt_put(rt);
 	sk->sk_route_caps = 0;
 	inet->inet_dport = 0;
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index e57b43006074..626166cb6d7e 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -985,6 +985,8 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 
 late_failure:
 	dccp_set_state(sk, DCCP_CLOSED);
+	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
+		inet_reset_saddr(sk);
 	__sk_dst_reset(sk);
 failure:
 	inet->inet_dport = 0;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 87d440f47a70..6a3a732b584d 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -343,6 +343,8 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	 * if necessary.
 	 */
 	tcp_set_state(sk, TCP_CLOSE);
+	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
+		inet_reset_saddr(sk);
 	ip_rt_put(rt);
 	sk->sk_route_caps = 0;
 	inet->inet_dport = 0;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 2a3f9296df1e..81b396e5cf79 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -359,6 +359,8 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 
 late_failure:
 	tcp_set_state(sk, TCP_CLOSE);
+	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
+		inet_reset_saddr(sk);
 failure:
 	inet->inet_dport = 0;
 	sk->sk_route_caps = 0;
-- 
2.30.2