Re: [PATCH v4 net 4/4] dccp/tcp: Fixup bhash2 bucket when connect() fails.

From:   Joanne Koong <[email protected]>
Date:   Mon, 21 Nov 2022 15:41:43 -0800
> On Fri, Nov 18, 2022 at 5:51 PM Kuniyuki Iwashima <[email protected]> wrote:
> >
> > If a socket bound to a wildcard address fails to connect(), we
> > only reset saddr and keep the port.  Then, we have to fix up the
> > bhash2 bucket; otherwise, the bucket has an inconsistent address
> > in the list.
> >
> > Also, listen() for such a socket will fire the WARN_ON() in
> > inet_csk_get_port(). [0]
> >
> > Note that when a system runs out of memory, we give up fixing the
> > bucket and unlink sk from bhash and bhash2 by inet_put_port().
> >
> > [0]:
> > WARNING: CPU: 0 PID: 207 at net/ipv4/inet_connection_sock.c:548 inet_csk_get_port (net/ipv4/inet_connection_sock.c:548 (discriminator 1))
> > Modules linked in:
> > CPU: 0 PID: 207 Comm: bhash2_prev_rep Not tainted 6.1.0-rc3-00799-gc8421681c845 #63
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.amzn2022.0.1 04/01/2014
> > RIP: 0010:inet_csk_get_port (net/ipv4/inet_connection_sock.c:548 (discriminator 1))
> > Code: 74 a7 eb 93 48 8b 54 24 18 0f b7 cb 4c 89 e6 4c 89 ff e8 48 b2 ff ff 49 8b 87 18 04 00 00 e9 32 ff ff ff 0f 0b e9 34 ff ff ff <0f> 0b e9 42 ff ff ff 41 8b 7f 50 41 8b 4f 54 89 fe 81 f6 00 00 ff
> > RSP: 0018:ffffc900003d7e50 EFLAGS: 00010202
> > RAX: ffff8881047fb500 RBX: 0000000000004e20 RCX: 0000000000000000
> > RDX: 000000000000000a RSI: 00000000fffffe00 RDI: 00000000ffffffff
> > RBP: ffffffff8324dc00 R08: 0000000000000001 R09: 0000000000000001
> > R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
> > R13: 0000000000000001 R14: 0000000000004e20 R15: ffff8881054e1280
> > FS:  00007f8ac04dc740(0000) GS:ffff88842fc00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020001540 CR3: 00000001055fa003 CR4: 0000000000770ef0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > PKRU: 55555554
> > Call Trace:
> >  <TASK>
> >  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)
> > RIP: 0033:0x7f8ac051de5d
> > Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 93 af 1b 00 f7 d8 64 89 01 48
> > RSP: 002b:00007ffc1c177248 EFLAGS: 00000206 ORIG_RAX: 0000000000000032
> > RAX: ffffffffffffffda RBX: 0000000020001550 RCX: 00007f8ac051de5d
> > RDX: ffffffffffffff80 RSI: 0000000000000000 RDI: 0000000000000004
> > RBP: 00007ffc1c177270 R08: 0000000000000018 R09: 0000000000000007
> > R10: 0000000020001540 R11: 0000000000000206 R12: 00007ffc1c177388
> > R13: 0000000000401169 R14: 0000000000403e18 R15: 00007f8ac0723000
> >  </TASK>
> >
> > Fixes: 28044fc1d495 ("net: Add a bhash2 table hashed by port and address")
> > Reported-by: syzbot <[email protected]>
> > Reported-by: Mat Martineau <[email protected]>
> > Signed-off-by: Kuniyuki Iwashima <[email protected]>
> 
> Acked-by: Joanne Koong <[email protected]>

Thanks for all your help!


> > ---
> >  include/net/inet_hashtables.h |  1 +
> >  net/dccp/ipv4.c               |  3 +--
> >  net/dccp/ipv6.c               |  3 +--
> >  net/dccp/proto.c              |  3 +--
> >  net/ipv4/inet_hashtables.c    | 38 +++++++++++++++++++++++++++++++----
> >  net/ipv4/tcp.c                |  3 +--
> >  net/ipv4/tcp_ipv4.c           |  3 +--
> >  net/ipv6/tcp_ipv6.c           |  3 +--
> >  8 files changed, 41 insertions(+), 16 deletions(-)
> >
> > diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
> > index ba06e8b52264..69174093078f 100644
> > --- a/include/net/inet_hashtables.h
> > +++ b/include/net/inet_hashtables.h
> > @@ -282,6 +282,7 @@ inet_bhash2_addr_any_hashbucket(const struct sock *sk, const struct net *net, in
> >   * rcv_saddr field should already have been updated when this is called.
> >   */
> >  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);
> > diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
> > index 95e376e3b911..b780827f5e0a 100644
> > --- a/net/dccp/ipv4.c
> > +++ b/net/dccp/ipv4.c
> > @@ -143,8 +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);
> > -       if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
> > -               inet_reset_saddr(sk);
> > +       inet_bhash2_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 94c101ed57a9..602f3432d80b 100644
> > --- a/net/dccp/ipv6.c
> > +++ b/net/dccp/ipv6.c
> > @@ -970,8 +970,7 @@ 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);
> > +       inet_bhash2_reset_saddr(sk);
> >         __sk_dst_reset(sk);
> >  failure:
> >         inet->inet_dport = 0;
> > diff --git a/net/dccp/proto.c b/net/dccp/proto.c
> > index c548ca3e9b0e..85e35c5e8890 100644
> > --- a/net/dccp/proto.c
> > +++ b/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);
> > diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
> > index 18ef370af113..3cec471a2cd2 100644
> > --- a/net/ipv4/inet_hashtables.c
> > +++ b/net/ipv4/inet_hashtables.c
> > @@ -871,7 +871,7 @@ static void inet_update_saddr(struct sock *sk, void *saddr, int family)
> >  #endif
> >  }
> >
> > -int inet_bhash2_update_saddr(struct sock *sk, void *saddr, int family)
> > +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;
> > @@ -883,7 +883,11 @@ int inet_bhash2_update_saddr(struct sock *sk, void *saddr, int family)
> >
> >         if (!inet_csk(sk)->icsk_bind2_hash) {
> >                 /* Not bind()ed before. */
> > -               inet_update_saddr(sk, saddr, family);
> > +               if (reset)
> > +                       inet_reset_saddr(sk);
> > +               else
> > +                       inet_update_saddr(sk, saddr, family);
> > +
> >                 return 0;
> >         }
> >
> > @@ -892,8 +896,19 @@ int inet_bhash2_update_saddr(struct sock *sk, void *saddr, int family)
> >          * 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);
> > +               }
> 
> nit: I think this is better placed in the dccp/tcp_ipv4/6 layer, to
> make it clear / more obvious that the sk gets unbinded in this edge
> case.

But it duplicates 2 calls (and a comment) across 6 places.

or we can move it to inet_bhash2_reset_saddr() like

void inet_bhash2_reset_saddr(struct sock *sk)
{
	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK) &&
	    __inet_bhash2_update_saddr(sk, NULL, 0, true) {
		inet_put_port(sk);
		inet_reset_saddr(sk);
	}
}
EXPORT_SYMBOL_GPL(inet_bhash2_reset_saddr);

I'm fine with whichever, which do you like ?

Or we can go as is and post a follow-up.


> 
> > +
> >                 return -ENOMEM;
> > +       }
> >
> >         bhash = inet_bhashfn(net, port, hinfo->bhash_size);
> >         head = &hinfo->bhash[bhash];
> > @@ -909,7 +924,10 @@ int inet_bhash2_update_saddr(struct sock *sk, void *saddr, int family)
> >         inet_bind2_bucket_destroy(hinfo->bind2_bucket_cachep, inet_csk(sk)->icsk_bind2_hash);
> >         spin_unlock(&head2->lock);
> >
> > -       inet_update_saddr(sk, saddr, family);
> > +       if (reset)
> > +               inet_reset_saddr(sk);
> > +       else
> > +               inet_update_saddr(sk, saddr, family);
> >
> >         head2 = inet_bhashfn_portaddr(hinfo, sk, net, port);
> >
> > @@ -930,8 +948,20 @@ int inet_bhash2_update_saddr(struct sock *sk, void *saddr, int family)
> >
> >         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
> > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> > index 54836a6b81d6..4f2205756cfe 100644
> > --- a/net/ipv4/tcp.c
> > +++ b/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);
> > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> > index 23dd7e9df2d5..da46357f501b 100644
> > --- a/net/ipv4/tcp_ipv4.c
> > +++ b/net/ipv4/tcp_ipv4.c
> > @@ -331,8 +331,7 @@ 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);
> > +       inet_bhash2_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 2f3ca3190d26..f0548dbcabd2 100644
> > --- a/net/ipv6/tcp_ipv6.c
> > +++ b/net/ipv6/tcp_ipv6.c
> > @@ -346,8 +346,7 @@ 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);
> > +       inet_bhash2_reset_saddr(sk);
> >  failure:
> >         inet->inet_dport = 0;
> >         sk->sk_route_caps = 0;
> > --
> > 2.30.2