netdev - Re: [PATCH v2 net 1/4] dccp/tcp: Reset saddr on failure after inet6?_hash

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Date:   Wed, 16 Nov 2022 16:43:23 -0800
From:   Joanne Koong <joannelkoong@...il.com>
To:     Kuniyuki Iwashima <kuniyu@...zon.com>
Cc:     acme@...driva.com, davem@...emloft.net, dccp@...r.kernel.org,
        dsahern@...nel.org, edumazet@...gle.com, kuba@...nel.org,
        kuni1840@...il.com, martin.lau@...nel.org,
        mathew.j.martineau@...ux.intel.com, netdev@...r.kernel.org,
        pabeni@...hat.com, pengfei.xu@...el.com,
        stephen@...workplumber.org, william.xuanziyang@...wei.com,
        yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH v2 net 1/4] dccp/tcp: Reset saddr on failure after inet6?_hash_connect().

On Wed, Nov 16, 2022 at 4:20 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> From:   Joanne Koong <joannelkoong@...il.com>
> Date:   Wed, 16 Nov 2022 16:11:21 -0800
> > On Wed, Nov 16, 2022 at 2:28 PM Kuniyuki Iwashima <kuniyu@...zon.com> 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 after 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 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
> > >
> > > 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>
> >
> > LGTM. Btw, the 4th patch in this series overwrites these changes by
> > moving this logic into the new inet_bhash2_reset_saddr() function you
> > added, so we could also drop this patch from the series. OTOH, this
> > commit message in this patch has some good background context. So I
> > don't have a preference either way :)
> >
> > Acked-by: Joanne Koong <joannelkoong@...il.com>
>
> Thanks for reviewing!
>
> Yes, these changes are overwritten later, but only this patch can be
> backported to other stable versions, so I kept this separated.
>

Gotcha, that makes sense! I will try to get my review of the other 2
patches by tomorrow or Friday.

Thanks for your work on this!

>
> > > ---
> > >  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