[PATCH 4.9 18/39] tcp: verify the checksum of the first data segment in a new connection

[Greg Kroah-Hartman]

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

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

From: Frank van der Linden <fllin...@amazon.com>

[ Upstream commit 4fd44a98ffe0d048246efef67ed640fdf2098a62 ]

commit 079096f103fa ("tcp/dccp: install syn_recv requests into ehash
table") introduced an optimization for the handling of child sockets
created for a new TCP connection.

But this optimization passes any data associated with the last ACK of the
connection handshake up the stack without verifying its checksum, because it
calls tcp_child_process(), which in turn calls tcp_rcv_state_process()
directly.  These lower-level processing functions do not do any checksum
verification.

Insert a tcp_checksum_complete call in the TCP_NEW_SYN_RECEIVE path to
fix this.

Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table")
Signed-off-by: Frank van der Linden <fllin...@amazon.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Tested-by: Balbir Singh <bsinghar...@gmail.com>
Reviewed-by: Balbir Singh <bsinghar...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/ipv4/tcp_ipv4.c |    4 ++++
 net/ipv6/tcp_ipv6.c |    4 ++++
 2 files changed, 8 insertions(+)

--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1661,6 +1661,10 @@ process:
                        reqsk_put(req);
                        goto discard_it;
                }
+               if (tcp_checksum_complete(skb)) {
+                       reqsk_put(req);
+                       goto csum_error;
+               }
                if (unlikely(sk->sk_state != TCP_LISTEN)) {
                        inet_csk_reqsk_queue_drop_and_put(sk, req);
                        goto lookup;
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1433,6 +1433,10 @@ process:
                        reqsk_put(req);
                        goto discard_it;
                }
+               if (tcp_checksum_complete(skb)) {
+                       reqsk_put(req);
+                       goto csum_error;
+               }
                if (unlikely(sk->sk_state != TCP_LISTEN)) {
                        inet_csk_reqsk_queue_drop_and_put(sk, req);
                        goto lookup;