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[PATCH 4.12 10/17] tcp: fastopen: tcp_connect() must refresh the route

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4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>


[ Upstream commit 8ba60924710cde564a3905588b6219741d6356d0 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/tcp_output.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3361,6 +3361,9 @@ int tcp_connect(struct sock *sk)
 	struct sk_buff *buff;
 	int err;
 
+	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
+		return -EHOSTUNREACH; /* Routing failure or similar. */
+
 	tcp_connect_init(sk);
 
 	if (unlikely(tp->repair)) {

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[PATCH 4.12 00/17] 4.12.7-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:10 +0200
  [PATCH 4.12 12/17] net: avoid skb_warn_bad_offload false positives on UFO Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 06/17] bpf, s390: fix jit branch offset related to ldimm64 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 15/17] packet: fix tp_reserve race in packet_set_ring Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 08/17] net: sched: set xt_tgchk_param par.net properly in ipt_init_target Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 14/17] udp: consistently apply ufo or fragmentation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 09/17] net: sched: set xt_tgchk_param par.nft_compat as 0 in ipt_init_target Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 16/17] scsi: sg: only check for dxfer_len greater than 256M Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 05/17] ipv6: set rt6i_protocol properly in the route when it is installed Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 10/17] tcp: fastopen: tcp_connect() must refresh the route Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 04/17] net: fix keepalive code vs TCP_FASTOPEN_CONNECT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 07/17] net/mlx4_en: dont set CHECKSUM_COMPLETE on SCTP packets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 02/17] ppp: fix xmit recursion detection on ppp channels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.12 03/17] tcp: avoid setting cwnd to invalid ssthresh after cwnd reduction states Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  Re: [PATCH 4.12 00/17] 4.12.7-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-08-12 04:00 +0200
    Re: [PATCH 4.12 00/17] 4.12.7-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 16:40 +0200
  Re: [PATCH 4.12 00/17] 4.12.7-stable review Guenter Roeck <linux@roeck-us.net> - 2017-08-12 14:30 +0200
    Re: [PATCH 4.12 00/17] 4.12.7-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 18:10 +0200

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