On Thu, Nov 3, 2022 at 10:24 AM Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> wrote: > > 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@xxxxxxxxxx/ > > Fixes: 3df80d9320bc ("[DCCP]: Introduce DCCPv6") > Fixes: 7c657876b63c ("[DCCP]: Initial implementation") > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> > --- > 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 > inet_reset_saddr() sets both inet_saddr and inet_rcv_saddr to 0, but I think there are some edge cases where when dccp/tcp_v4/6_connect() is called, inet_saddr is 0 but inet_rcv_saddr is not, which means we'd need to reset inet_rcv_saddr to its original value. The example case I'm looking at is __inet_bind() where if the request is to bind to a multicast address, inet->inet_rcv_saddr = inet->inet_saddr = addr->sin_addr.s_addr; if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST) inet->inet_saddr = 0; /* Use device */