Re: [RFC] bhash2 and WARN_ON() for inconsistent sk saddr.

[Joanne Koong <joannelkoong@gmail.com>]

On Tue, Nov 8, 2022 at 2:45 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>
> From:   Joanne Koong <joannelkoong@gmail.com>
> Date:   Tue, 8 Nov 2022 14:02:11 -0800
> > On Tue, Nov 8, 2022 at 11:50 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
> > >
> > > From:   Joanne Koong <joannelkoong@gmail.com>
> > > Date:   Tue, 8 Nov 2022 09:40:22 -0800
> > > >  On Mon, Nov 7, 2022 at 5:27 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
> > > > >
> > > > > From:   Joanne Koong <joannelkoong@gmail.com>
> > > > > Date:   Mon, 7 Nov 2022 14:20:46 -0800
> > > > > > On Fri, Oct 28, 2022 at 5:13 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
> > > > > > >
> > > > > > > Hi,
> > > > > > >
> > > > > > > I want to discuss bhash2 and WARN_ON() being fired every day this month
> > > > > > > on my syzkaller instance without repro.
> > > > > > >
> > > > > > >   WARNING: CPU: 0 PID: 209 at net/ipv4/inet_connection_sock.c:548 inet_csk_get_port (net/ipv4/inet_connection_sock.c:548 (discriminator 1))
> > > > > > >   ...
> > > > > > >   inet_csk_listen_start (net/ipv4/inet_connection_sock.c:1205)
> > > > > > >   inet_listen (net/ipv4/af_inet.c:228)
> > > > > > >   __sys_listen (net/socket.c:1810)
> > > > > > >   __x64_sys_listen (net/socket.c:1819 net/socket.c:1817 net/socket.c:1817)
> > > > > > >   do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80)
> > > > > > >   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)
> > > > > > >
> > > > > > [...]
> > > > > > >
> > > > > > > Please see the source addresses of s2/s3 below after connect() fails.
> > > > > > > The s2 case is another variant of the first syzbot report, which has
> > > > > > > been already _fixed_.  And the s3 case is a repro for the issue that
> > > > > > > Mat and I saw.
> > > > > >
> > > > > > Since the s2 address mismatch case is addressed by your patch
> > > > > > https://lore.kernel.org/netdev/20221103172419.20977-1-kuniyu@amazon.com/,
> > > > > > I will focus my comments here on the s3 case.
> > > > > >
> > > > > > >
> > > > > > >   # sysctl -w net.ipv4.tcp_syn_retries=1
> > > > > > >   net.ipv4.tcp_syn_retries = 1
> > > > > > >   # python3
> > > > > > >   >>> from socket import *
> > > > > > >   >>>
> > > > > > >   >>> s1 = socket()
> > > > > > >   >>> s1.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
> > > > > > >   >>> s1.bind(('0.0.0.0', 10000))
> > > > > > >   >>> s1.connect(('127.0.0.1', 10000))
> > > > > > >   >>>
> > > > > > >   >>> s2 = socket()
> > > > > > >   >>> s2.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
> > > > > > >   >>> s2.bind(('0.0.0.0', 10000))
> > > > > > >   >>> s2
> > > > > > >   <socket.socket fd=4, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('0.0.0.0', 10000)>
> > > > > > >   >>>
> > > > > > >   >>> s2.connect(('127.0.0.1', 10000))
> > > > > > >   Traceback (most recent call last):
> > > > > > >     File "<stdin>", line 1, in <module>
> > > > > > >   OSError: [Errno 99] Cannot assign requested address
> > > > > > >   >>>
> > > > > > >   >>> s2
> > > > > > >   <socket.socket fd=4, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('127.0.0.1', 10000)>
> > > > > > >                                                                                                    ^^^ ???
> > > > > > >   >>> s3 = socket()
> > > > > > >   >>> s3.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
> > > > > > >   >>> s3.bind(('0.0.0.0', 10000))
> > > > > > >   >>> s3
> > > > > > >   <socket.socket fd=5, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('0.0.0.0', 10000)>
> > > > > > >   >>>
> > > > > > >   >>> s3.connect(('0.0.0.1', 1))
> > > > > > >   Traceback (most recent call last):
> > > > > > >     File "<stdin>", line 1, in <module>
> > > > > > >   TimeoutError: [Errno 110] Connection timed out
> > > > > > >   >>>
> > > > > > >   >>> s3
> > > > > > >   <socket.socket fd=5, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('0.0.0.0', 10000)>
> > > > > > >
> > > > > > > We can fire the WARN_ON() by s3.listen().
> > > > > > >
> > > > > > >   >>> s3.listen()
> > > > > > >   [ 1096.845905] ------------[ cut here ]------------
> > > > > > >   [ 1096.846290] WARNING: CPU: 0 PID: 209 at net/ipv4/inet_connection_sock.c:548 inet_csk_get_port+0x6bb/0x9e0
> > > > > >
> > > > > > I'm on the head of net-next/master (commit
> > > > > > bf46390f39c686d62afeae9845860e63886d63b) and trying to repro this
> > > > > > locally, but the warning isn't showing up for me after following the
> > > > > > steps above. Not sure why.
> > > > >
> > > > > Hmm... it reproduced on top of the commit.  I'm testing on QEMU and login
> > > > > to serial console which outputs syslog in the same stream, so you may want
> > > > > to check /var/log/messages or something.
> > > > >
> > > > > ---8<---
> > > > > # sysctl -w net.ipv4.tcp_syn_retries=1
> > > > > # python3
> > > > > >>> from socket import *
> > > > > >>>
> > > > > >>> s = socket()
> > > > > >>> s.bind(('0', 10000))
> > > > > >>> s.connect(('0.0.0.1', 1))
> > > > > Traceback (most recent call last):
> > > > >   File "<stdin>", line 1, in <module>
> > > > > TimeoutError: [Errno 110] Connection timed out
> > > > > >>> s
> > > > > <socket.socket fd=3, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('0.0.0.0', 10000)>
> > > > > >>> s.listen(32)
> > > > > [   96.598308] ------------[ cut here ]------------
> > > > > [   96.598598] WARNING: CPU: 0 PID: 214 at net/ipv4/inet_connection_sock.c:548 inet_csk_get_port+0x6bb/0x9e0
> > > > > ...
> > > > >
> > > > > >>> s = socket()
> > > > > >>> s.bind(('0', 10001))
> > > > > >>> s.connect(('localhost', 1))
> > > > > Traceback (most recent call last):
> > > > >   File "<stdin>", line 1, in <module>
> > > > > ConnectionRefusedError: [Errno 111] Connection refused
> > > > > >>> s.listen(32)
> > > > > [  139.157193] ------------[ cut here ]------------
> > > > > [  139.157528] WARNING: CPU: 0 PID: 214 at net/ipv4/inet_connection_sock.c:548 inet_csk_get_port+0x6bb/0x9e0
> > > > > ---8<---
> > > > >
> > > > >
> > > > > >
> > > > > > >
> > > > > > > In the s3 case, connect() resets sk->sk_rcv_saddr to INADDR_ANY without
> > > > > > > updating the bhash2 bucket; OTOH sk has the correct non-NULL bhash bucket.
> > > > > >
> > > > > > To summarize, the path you are talking about is tcp_v4_connect() in
> > > > > > kernel/linux/net/ipv4/tcp_ipv4.c where the sk originally has saddr
> > > > > > INADDR_ANY, the sk gets assigned a new address, that new address gets
> > > > > > updated in the bhash2 table, and then when inet_hash_connect() is
> > > > > > called, it fails which brings us to the "goto failure". In the failure
> > > > > > goto, we call "tcp_set_state(sk, TCP_CLOSE)" but in the case where
> > > > > > "SOCK_BINDPORT_LOCK" is held, "inet_put_port(sk)" is *not* called,
> > > > > > which means the sk will still be in the bhash2 table with the new
> > > > > > address.
> > > > >
> > > > > Correct.
> > > > >
> > > > > More precisely, 3 functions after inet_hash_connect() can cause the same
> > > > > issue.
> > > > >
> > > > > - ip_route_newports
> > > > > - tcp_fastopen_defer_connect
> > > > > - tcp_connect
> > > > >
> > > > >
> > > > > >
> > > > > > > So, when we call listen() for s3, inet_csk_get_port() does not call
> > > > > > > inet_bind_hash() and the WARN_ON() for bhash2 fires.
> > > > > > >
> > > > > > >   if (!inet_csk(sk)->icsk_bind_hash)
> > > > > > >         inet_bind_hash(sk, tb, tb2, port);
> > > > > > >   WARN_ON(inet_csk(sk)->icsk_bind_hash != tb);
> > > > > > >   WARN_ON(inet_csk(sk)->icsk_bind2_hash != tb2);
> > > > > > >
> > > > > > [...]
> > > > > > >
> > > > > > > In the s3 case, connect() falls into a different path.  We reach the
> > > > > > > sock_error label in __inet_stream_connect() and call sk_prot->disconnect(),
> > > > > > > which resets sk->sk_rcv_saddr.
> > > > > >
> > > > > > This is the case where in __inet_stream_connect(), the call to
> > > > > > "sk->sk_prot->connect()" succeeds but then the connection is closed by
> > > > > > RST/timeout/ICMP error, so then the "goto sock_error" is triggered,
> > > > > > correct?
> > > > >
> > > > > Yes.
> > > > >
> > > > >
> > > > > >
> > > > > > >
> > > > > > > Then, there could be two subsequent issues.
> > > > > > >
> > > > > > >   * listen() leaks a newly allocated bhash2 bucket
> > > > > > >
> > > > > > >   * In inet_put_port(), inet_bhashfn_portaddr() computes a wrong hash for
> > > > > > >     inet_csk(sk)->icsk_bind2_hash, resulting in list corruption.
> > > > > > >
> > > > > > > We can fix these easily but it still leaves inconsistent sockets in bhash2,
> > > > > > > so we need to fix the root cause.
> > > > > > >
> > > > > > > As a side note, this issue only happens when we bind() only port before
> > > > > > > connect().  If we do not bind() port, tcp_set_state(sk, TCP_CLOSE) calls
> > > > > > > inet_put_port() and unhashes the sk from bhash2.
> > > > > > >
> > > > > > >
> > > > > > > At first, I applied the patch below so that both sk2 and sk3 trigger
> > > > > > > WARN_ON().  Then, I tried two approaches:
> > > > > > >
> > > > > > >   * Fix up the bhash2 entry when calling sk_rcv_saddr
> > > > > > >
> > > > > > >   * Change the bhash2 entry only when connect() succeeds
> > > > > > >
> > > > > > > The former does not work when we run out of memory.  When we change saddr
> > > > > > > from INADDR_ANY, inet_bhash2_update_saddr() could free (INADDR_ANY, port)
> > > > > > > bhash2 bucket.  Then, we possibly could not allocate it again when
> > > > > > > restoring saddr in the failure path.
> > > > > > >
> > > > > > > The latter does not work when a sk is in non-blocking mode.  In this case,
> > > > > > > a user might not call the second connect() to fix up the bhash2 bucket.
> > > > > > >
> > > > > > >   >>> s4 = socket()
> > > > > > >   >>> s4.bind(('0.0.0.0', 10000))
> > > > > > >   >>> s4.setblocking(False)
> > > > > > >   >>> s4
> > > > > > >   <socket.socket fd=3, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('0.0.0.0', 10000)>
> > > > > > >
> > > > > > >   >>> s4.connect(('0.0.0.1', 1))
> > > > > > >   Traceback (most recent call last):
> > > > > > >     File "<stdin>", line 1, in <module>
> > > > > > >   BlockingIOError: [Errno 115] Operation now in progress
> > > > > > >   >>> s4
> > > > > > >   <socket.socket fd=3, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('10.0.2.15', 10000)>
> > > > > > >
> > > > > > > Also, the former approach does not work for the non-blocking case.  Let's
> > > > > > > say the second connect() fails.  What if we fail to allocate an INADDR_ANY
> > > > > > > bhash2 bucket?  We have to change saddr to INADDR_ANY but cannot.... but
> > > > > > > the connect() actually failed....??
> > > > > > >
> > > > > > >   >>> s4.connect(('0.0.0.1', 1))
> > > > > > >   Traceback (most recent call last):
> > > > > > >     File "<stdin>", line 1, in <module>
> > > > > > >   ConnectionRefusedError: [Errno 111] Connection refused
> > > > > > >   >>> s4
> > > > > > >   <socket.socket fd=3, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('0.0.0.0', 10000)>
> > > > > > >
> > > > > > >
> > > > > > > Now, I'm thinking bhash2 bucket needs a refcnt not to be freed while
> > > > > > > refcnt is greater than 1.  And we need to change the conflict logic
> > > > > > > so that the kernel ignores empty bhash2 bucket.  Such changes could
> > > > > > > be big for the net tree, but the next LTS will likely be v6.1 which
> > > > > > > has bhash2.
> > > > > > >
> > > > > > > What do you think is the best way to fix the issue?
> > > > > >
> > > > > > To summarize your analysis, there is an issue right now where for
> > > > > > sockets that are binded on address INADDR_ANY,  we need to handle the
> > > > > > error case where if a connection fails and SOCK_BINDPORT_LOCK is held,
> > > > > > the new address it was assigned needs to be taken out of bhash2 and
> > > > > > the original address (INADDR_ANY) needs to be re-added to bhash2.
> > > > > > There are two of these error cases we need to handle,  as you
> > > > > > mentioned above - 1) in dccp/tcp_v4_connect() where the connect call
> > > > > > fails and 2) in __inet_stream_connect() where the connect call
> > > > > > succeeds but the connection is closed by a RST/timeout/ICMP error.
> > > > > >
> > > > > > I think the simplest solution is to modify inet_bhash2_update_saddr()
> > > > > > so that we don't free the inet_bind2_bucket() for INADDR_ANY/port (if
> > > > > > it is empty after we update the saddr to the new addr) *until* the
> > > > > > connect succeeds. When the connect succeeds, then we can check whether
> > > > > > the inet_bind2_bucket for INADDR_ANY is empty, and if it is, then do
> > > > > > the freeing for it.
> > > > > >
> > > > > > What are your thoughts on this?
> > > > >
> > > > > I was thinking the same, but this scenario will break it ?
> > > > >
> > > > >   connect() <-- unblocking socket
> > > > >     return -EINPROGRESS
> > > > >
> > > > >   receive SYN+ACK, send back ACK, and set state to TCP_ESTABLISEHD
> > > > >
> > > > >   free the old INADDR_ANY bucket
> > > > >
> > > > >   get RST and set state to TCP_CLOSE
> > > > >
> > > > >   connect()
> > > > >     goto sock_error and ->disconect() fail to restore the bucket
> > > > >
> > >
> > > I meant all of the above happen at the client side, so the server-side
> > > code is orthogonal.
> > >
> > > But I got your point.  I've misunderstood "When the connect succeeds".
> > > I was thinking that we'll free bhash2 bucket in the fast path where we
> > > send back SYN+ACK to the server.  OTOH, you meant it to be when the
> > > connect() syscall returns 0, right ?
> > >
> > > Then, I think it's doable, like
> > >
> > >   1) inet_bhash2_update_saddr() increments addrany_tb2->connecting
> > >
> > >   2) when connect() succeeds,
> > >
> > >      if (dec_and_test(&addrany_tb2->connecting) && is_empty(addrany_tb2->owners))
> > >          free(addrany_tb2);
> > >
> > >   3) while close()ing,
> > >
> > >      tb2 = ...
> > >      addrany_tb2 = ...
> > >
> > >      if ((sk->sk_user_locks & SOCK_BINDPORT_LOCK) &&
> > >          !(sk->sk_user_locks & SOCK_BINDADDR_LOCK) &&
> > >          tb2 != addrany_tb2 &&
> > >          sock->state != SS_CONNECTED &&
> > >          dec_and_test(&addrany_tb2->connecting) &&
> > >          is_empty(addrany_tb2->owners))
> > >          free(addrany_tb2)
> > >
> > > More consideration would be needed for inet_shutdown() etc though.
> >
> > Sorry, my terminology was ambiguous :) By "when the connect succeeds",
> > I meant when the call to tcp_connect() succeeds at the end of
> > tcp_v4_connect().
> >
> > There are 2 cases you brought up regarding connection failures on
> > binded INADDR_ANY sockets that might lead to a bhash2 mismatch:
> >
> > #1) in dccp/tcp_v4_connect() where an error leads to the "goto failure"
> > #2) in __inet_stream_connect() where an error leads to the "goto sock_error"
> >
> > Regarding #2, I don't think this leads to a bhash2 mismatch. The "goto
> > sock_error" triggers disconnect() and the disconnect() call will
> > always remove the socket from the bhash and bhash2 tables since the
> > socket when it was cloned had the SOCK_BINDPORT_LOCK flag unset.
>
> I think client sockets are not cloned.  The clone code is to create
> a child socket from a listener when receiving an ACK for SYN+ACK or
> earlier fastopen stage.

Gotcha, thanks for clarifying.

This edge case only happens when this situation occurs:
A socket is bound to INADDR_ANY on a specified port -> socket makes a
connect() call -> we run into one of these scenarios: the error case
in dccp/tcp_v4/6_connect() or error case in __inet_stream_connect() or
call to inet_shutdown()) -> in handling that error case, we remove
socket from bhash2's new address/port table, and try to add it to the
bhash2's INADDR_ANY/port table -> there is a "not enough memory" error
in the case where the INADDR_ANY/port table got previously freed and
we try to re-allocate it with kmem_cache_alloc()

I think the best solution is to unbind the socket if this situation
happens, because

1) The socket will have to be unbinded in other error cases.

After looking at the code some more, I believe there's an existing bug
when resetting the socket address back to INADDR_ANY after an error
occurs (while BIND_PORTLOCK is set). The socket's address *cannot*
simply be reset back to 0 without removing it from the bhash table,
without first checking whether this leads to a bind conflict. For
example, there could be this scenario: socket 1 binds to INADDR_ANY on
port 443, there is no bind conflict (for example, no other sockets are
binded to port 443), the connect succeeds and socket1 is now assigned
address 1234 on port 443, then socket2 connects to port 443 on some
other address, there's an error that causes socket1's connection to
close and socket1's address is now reset back to INADDR_ANY. However,
socket1's address cannot be reset back to INADDR_ANY on port 443
because now there is a conflict with socket2 if socket1's address is
INADDR_ANY.

Thus, we need to check whether there would be a bind conflict before
resetting the socket's address back to INADDR_ANY. And if there is,
then we'd need to unbind socket1.

I think this fix should be in a separate patchset from any bhash2 changes.


2) If the "-ENOMEM" case is hit in the kmem_cache_alloc(), I believe
this only happens if the system is out of memory, in which case I
think the socket will most likely be ineffective anyways (eg system
reboots)

3) This situation is a very rare corner case. I don't think it's worth
providing the optimal solution for, by making the common case more
complex (for example, not including INADDR_ANY entries in bhash2 and
putting them at the front of the list in bhash, as suggested by Martin
in a previous reply, which seems like the best solution if we were to
fix this optimally)


I propose that we do the following:
in the error cases in dccp/tcp_v4/6_connect(), __inet_stream_connect()
and inet_shutdown() where the socket's address needs to get reset back
to INADDR_ANY, we remove the socket (from socket's new address + port)
from the bhash2 table. Then we add the socket to the bhash2 table
using INADDR_ANY + port; in the unlikely case where this operation
fails due to -ENOMEM, then we unbind the socket.

What are your thoughts?

>
> When a client socket receives a SYN+ACK,
>
>   tcp_v4_rcv
>     tcp_v4_do_rcv
>       tcp_rcv_state_process
>         tcp_rcv_synsent_state_process
>           tcp_finish_connect <-- just set TCP_ESTABLISHED
>
> there's no clone, so tcp_disconnect() will not unhash sk from bhash2
> if the sk is bound to INADDR_ANY.
>
> Even if #1 succeeds, #2 could fail after, thus we have to take care
> of #2 at the same time.
>
> So, I think the only place we can free the addrany_tb2 is just after
> "sock->state = SS_CONNECTED;" in __inet_stream_connect().
>
>
> > For #1, I think the simplest way to handle this is to not free the
> > inet_bind2_bucket for INADDR_ANY/port when we call
> > inet_bhash2_update_saddr(). Then, at the end of the
> > dccp/tcp_v4/6_connect() call, if it is successful, we free the
> > INADDR_ANY/port inet_bind2_bucket if it's empty. And if that is not
> > successful and there was a failure somewhere, then in the "goto
> > failure", we remove the socket from the new_addr bind bucket / clean
> > up the new_addr bind bucket and re-add the socket back to the
> > INADDR_ANY bind bucket.
> >
> > What are your thoughts?
> >
> > >
> > >
> > > > I don't think this scenario will break it because after a successful
> > > > connect call, a disconnect will remove the socket from the bhash (and
> > > > bhash2) table altogether since the socket will *not* have
> > > > SOCK_BINDPORT_LOCK set.
> > > >
> > > > This is the code path I'm looking at:
> > > >
> > > > connect call is successful and the three way handshake has completed
> > > > -> tcp_v4_syn_recv_sock() is called where we create the new socket
> > > > tcp_v4_syn_recv_sock() -> tcp_create_openreq_child() ->
> > > > inet_csk_clone_lock() -> sk_clone_lock()
> > > >
> > > > In sk_clone_lock(), we create a newsk where newsk->sk_userlocks will
> > > > *not* have the SOCK_BINDPORT_LOCK flag set (newsk->sk_userlocks =
> > > > sk->sk_userlocks & ~SOCK_BINDPORT_LOCK;).
> > > >
> > > > If the connection gets closed by a RST/timeout/ICMP error, then this
> > > > socket will go through disconnect() where in the disconnect call, it
> > > > will remove the socket from the bhash and bhash2 tables. For example,
> > > > for tcp, this code path is tcp_disconnect() -> tcp_set_state(sk,
> > > > TCP_CLOSE) -> inet_put_port() - this is also verified by the
> > > > "WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);" at the end of
> > > > tcp_disconnect().
> > > >
> > > > What are your thoughts?
> > > >
> > > > >
> > > > > >
> > > > > > Thank you.
> > > > > >
> > > > > > >
> > > > > > > Thank you.
> > > > > > >
> > > > > > >
> > > > > > > ---8<---
> > > > > > > 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 7a250ef9d1b7..834245da1e95 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;
> > > > > > > ---8<---