[PATCH net] tcp: fastopen: tcp_connect() must refresh the route

[PATCH net] tcp: fastopen: tcp_connect() must refresh the route

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

With new TCP_FASTOPEN_CONNECT socket option, there is a possibility
to call tcp_connect() while socket sk_dst_cache is either NULL
or invalid.

 +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
 +0 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0
 +0 setsockopt(4, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0
 +0 connect(4, ..., ...) = 0

<< sk->sk_dst_cache becomes obsolete, or even set to NULL >>

 +1 sendto(4, ..., 1000, MSG_FASTOPEN, ..., ...) = 1000


We need to refresh the route otherwise bad things can happen,
especially when syzkaller is running on the host :/

Fixes: 19f6d3f3c8422 ("net/tcp-fastopen: Add new API support")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Wei Wang <weiwan@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
---
 net/ipv4/tcp_output.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 276406a83a37..b7661a68d498 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3436,6 +3436,10 @@ int tcp_connect(struct sock *sk)
 	int err;
 
 	tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB);
+
+	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
+		return -EHOSTUNREACH; /* Routing failure or similar. */
+
 	tcp_connect_init(sk);
 
 	if (unlikely(tp->repair)) {

Re: [PATCH net] tcp: fastopen: tcp_connect() must refresh the route

[Wei Wang]

On Tue, Aug 8, 2017 at 1:41 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> From: Eric Dumazet <edumazet@google.com>
>
> With new TCP_FASTOPEN_CONNECT socket option, there is a possibility
> to call tcp_connect() while socket sk_dst_cache is either NULL
> or invalid.
>
>  +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
>  +0 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0
>  +0 setsockopt(4, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0
>  +0 connect(4, ..., ...) = 0
>
> << sk->sk_dst_cache becomes obsolete, or even set to NULL >>
>
>  +1 sendto(4, ..., 1000, MSG_FASTOPEN, ..., ...) = 1000
>
>
> We need to refresh the route otherwise bad things can happen,
> especially when syzkaller is running on the host :/
>
> Fixes: 19f6d3f3c8422 ("net/tcp-fastopen: Add new API support")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Wei Wang <weiwan@google.com>
> Cc: Yuchung Cheng <ycheng@google.com>
> ---

Thanks a lot for the fix, Eric.

Acked-by: Wei Wang <weiwan@google.com>

Re: [PATCH net] tcp: fastopen: tcp_connect() must refresh the route

[Yuchung Cheng]

On Tue, Aug 8, 2017 at 1:41 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> From: Eric Dumazet <edumazet@google.com>
>
> With new TCP_FASTOPEN_CONNECT socket option, there is a possibility
> to call tcp_connect() while socket sk_dst_cache is either NULL
> or invalid.
>
>  +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
>  +0 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0
>  +0 setsockopt(4, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0
>  +0 connect(4, ..., ...) = 0
>
> << sk->sk_dst_cache becomes obsolete, or even set to NULL >>
>
>  +1 sendto(4, ..., 1000, MSG_FASTOPEN, ..., ...) = 1000
>
>
> We need to refresh the route otherwise bad things can happen,
> especially when syzkaller is running on the host :/
>
> Fixes: 19f6d3f3c8422 ("net/tcp-fastopen: Add new API support")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Wei Wang <weiwan@google.com>
> Cc: Yuchung Cheng <ycheng@google.com>
> ---
Acked-by: Yuchung Cheng <ycheng@google.com>

Thanks for the fix!

>  net/ipv4/tcp_output.c |    4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 276406a83a37..b7661a68d498 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -3436,6 +3436,10 @@ int tcp_connect(struct sock *sk)
>         int err;
>
>         tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB);
> +
> +       if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
> +               return -EHOSTUNREACH; /* Routing failure or similar. */
> +
>         tcp_connect_init(sk);
>
>         if (unlikely(tp->repair)) {
>
>

Re: [PATCH net] tcp: fastopen: tcp_connect() must refresh the route

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 08 Aug 2017 01:41:58 -0700

> From: Eric Dumazet <edumazet@google.com>
> 
> With new TCP_FASTOPEN_CONNECT socket option, there is a possibility
> to call tcp_connect() while socket sk_dst_cache is either NULL
> or invalid.
> 
>  +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
>  +0 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0
>  +0 setsockopt(4, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0
>  +0 connect(4, ..., ...) = 0
> 
> << sk->sk_dst_cache becomes obsolete, or even set to NULL >>
> 
>  +1 sendto(4, ..., 1000, MSG_FASTOPEN, ..., ...) = 1000
> 
> 
> We need to refresh the route otherwise bad things can happen,
> especially when syzkaller is running on the host :/
> 
> Fixes: 19f6d3f3c8422 ("net/tcp-fastopen: Add new API support")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied and queued up for -stable.