tcp: Do not call IPv4 specific func in tcp_check_req

Calling IPv4 specific inet_csk_route_req in tcp_check_req
is a bad idea and crashes machine on IPv6 connections, as reported
by Valdis Kletnieks

Also, all we are really interested in is the timestamp
option in the header, so calling tcp_parse_options()
with the "estab" set to false flag is an overkill as
it tries to parse half a dozen other TCP options.

We know whether timestamp should be enabled or not
using data from request_sock.

Signed-off-by: Gilad Ben-Yossef <gilad@codefidence.com>
Tested-by: Valdis.Kletnieks@vt.edu
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 6 deletions

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 463d51b53d37..a9d34e224cb6 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -500,11 +500,10 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
         int paws_reject = 0;
         struct tcp_options_received tmp_opt;
         struct sock *child;
-        struct dst_entry *dst = inet_csk_route_req(sk, req);
 
-        tmp_opt.saw_tstamp = 0;
-        if (th->doff > (sizeof(struct tcphdr)>>2)) {
-                tcp_parse_options(skb, &tmp_opt, 0, dst);
+        if ((th->doff > (sizeof(struct tcphdr)>>2)) && (req->ts_recent)) {
+                tmp_opt.tstamp_ok = 1;
+                tcp_parse_options(skb, &tmp_opt, 1, NULL);
 
                 if (tmp_opt.saw_tstamp) {
                         tmp_opt.ts_recent = req->ts_recent;
@@ -517,8 +516,6 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
                 }
         }
 
-        dst_release(dst);
-
         /* Check for pure retransmitted SYN. */
         if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn &&
             flg == TCP_FLAG_SYN &&