[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 <fllinden@xxxxxxxxxx>

[ 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 <fllinden@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Tested-by: Balbir Singh <bsingharora@xxxxxxxxx>
Reviewed-by: Balbir Singh <bsingharora@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 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;