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    Subject[PATCH 046/173] tcp: Increase TCP_MAXSEG socket option minimum.
    2.6.27.59-stable review patch.  If anyone has any objections, please let us know.

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

    From: David S. Miller <davem@davemloft.net>

    commit 7a1abd08d52fdeddb3e9a5a33f2f15cc6a5674d2 upstream.

    As noted by Steve Chen, since commit
    f5fff5dc8a7a3f395b0525c02ba92c95d42b7390 ("tcp: advertise MSS
    requested by user") we can end up with a situation where
    tcp_select_initial_window() does a divide by a zero (or
    even negative) mss value.

    The problem is that sometimes we effectively subtract
    TCPOLEN_TSTAMP_ALIGNED and/or TCPOLEN_MD5SIG_ALIGNED from the mss.

    Fix this by increasing the minimum from 8 to 64.

    Reported-by: Steve Chen <schen@mvista.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Cc: Moritz Muehlenhoff <jmm@debian.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    net/ipv4/tcp.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/net/ipv4/tcp.c
    +++ b/net/ipv4/tcp.c
    @@ -2117,7 +2117,7 @@ static int do_tcp_setsockopt(struct sock
    /* Values greater than interface MTU won't take effect. However
    * at the point when this call is done we typically don't yet
    * know which interface is going to be used */
    - if (val < 8 || val > MAX_TCP_WINDOW) {
    + if (val < 64 || val > MAX_TCP_WINDOW) {
    err = -EINVAL;
    break;
    }



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