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    Subject[PATCH 4.9 18/39] tcp: verify the checksum of the first data segment in a new connection
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Frank van der Linden <fllinden@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 <fllinden@amazon.com>
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Tested-by: Balbir Singh <bsingharora@gmail.com>
    Reviewed-by: Balbir Singh <bsingharora@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@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;

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