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    Subject[PATCH 4.9 35/54] tcp: memset ca_priv data to 0 properly
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Wei Wang <weiwan@google.com>


    [ Upstream commit c1201444075009507a6818de6518e2822b9a87c8 ]

    Always zero out ca_priv data in tcp_assign_congestion_control() so that
    ca_priv data is cleared out during socket creation.
    Also always zero out ca_priv data in tcp_reinit_congestion_control() so
    that when cc algorithm is changed, ca_priv data is cleared out as well.
    We should still zero out ca_priv data even in TCP_CLOSE state because
    user could call connect() on AF_UNSPEC to disconnect the socket and
    leave it in TCP_CLOSE state and later call setsockopt() to switch cc
    algorithm on this socket.

    Fixes: 2b0a8c9ee ("tcp: add CDG congestion control")
    Reported-by: Andrey Konovalov <andreyknvl@google.com>
    Signed-off-by: Wei Wang <weiwan@google.com>
    Acked-by: Eric Dumazet <edumazet@google.com>
    Acked-by: Yuchung Cheng <ycheng@google.com>
    Acked-by: Neal Cardwell <ncardwell@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv4/tcp_cong.c | 11 +++--------
    1 file changed, 3 insertions(+), 8 deletions(-)

    --- a/net/ipv4/tcp_cong.c
    +++ b/net/ipv4/tcp_cong.c
    @@ -167,12 +167,8 @@ void tcp_assign_congestion_control(struc
    }
    out:
    rcu_read_unlock();
    + memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));

    - /* Clear out private data before diag gets it and
    - * the ca has not been initialized.
    - */
    - if (ca->get_info)
    - memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
    if (ca->flags & TCP_CONG_NEEDS_ECN)
    INET_ECN_xmit(sk);
    else
    @@ -199,11 +195,10 @@ static void tcp_reinit_congestion_contro
    tcp_cleanup_congestion_control(sk);
    icsk->icsk_ca_ops = ca;
    icsk->icsk_ca_setsockopt = 1;
    + memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));

    - if (sk->sk_state != TCP_CLOSE) {
    - memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
    + if (sk->sk_state != TCP_CLOSE)
    tcp_init_congestion_control(sk);
    - }
    }

    /* Manage refcounts on socket close. */

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