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    Subject[PATCH 3.11 133/137] tcp: Fix integer-overflow in TCP vegas
    Date
    3.11.10.15 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Christoph Paasch <christoph.paasch@uclouvain.be>

    commit 1f74e613ded11517db90b2bd57e9464d9e0fb161 upstream.

    In vegas we do a multiplication of the cwnd and the rtt. This
    may overflow and thus their result is stored in a u64. However, we first
    need to cast the cwnd so that actually 64-bit arithmetic is done.

    Then, we need to do do_div to allow this to be used on 32-bit arches.

    Cc: Stephen Hemminger <stephen@networkplumber.org>
    Cc: Neal Cardwell <ncardwell@google.com>
    Cc: Eric Dumazet <eric.dumazet@gmail.com>
    Cc: David Laight <David.Laight@ACULAB.COM>
    Cc: Doug Leith <doug.leith@nuim.ie>
    Fixes: 8d3a564da34e (tcp: tcp_vegas cong avoid fix)
    Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    net/ipv4/tcp_vegas.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
    index 80fa2bfd7ede..c042e529a11e 100644
    --- a/net/ipv4/tcp_vegas.c
    +++ b/net/ipv4/tcp_vegas.c
    @@ -218,7 +218,8 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
    * This is:
    * (actual rate in segments) * baseRTT
    */
    - target_cwnd = tp->snd_cwnd * vegas->baseRTT / rtt;
    + target_cwnd = (u64)tp->snd_cwnd * vegas->baseRTT;
    + do_div(target_cwnd, rtt);

    /* Calculate the difference between the window we had,
    * and the window we would like to have. This quantity
    --
    1.9.1


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