tcp: fastopen: tcp_connect() must refresh the route

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: Wei Wang <weiwan@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 276406a83a37efd0aa21cc4647cd9ac873bff96d..b7661a68d4984c485a4853441d21abe8da9e325a 100644 (file)
--- 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)) {