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    Subject[PATCH 3.10 03/24] ipv6: reset dst.expires value when clearing expire flag
    Date
    3.10-stable review patch.  If anyone has any objections, please let me know.

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

    From: Hannes Frederic Sowa <hannes@stressinduktion.org>

    [ Upstream commit 01ba16d6ec85a1ec4669c75513a76b61ec53ee50 ]

    On receiving a packet too big icmp error we update the expire value by
    calling rt6_update_expires. This function uses dst_set_expires which is
    implemented that it can only reduce the expiration value of the dst entry.

    If we insert new routing non-expiry information into the ipv6 fib where
    we already have a matching rt6_info we only clear the RTF_EXPIRES flag
    in rt6i_flags and leave the dst.expires value as is.

    When new mtu information arrives for that cached dst_entry we again
    call dst_set_expires. This time it won't update the dst.expire value
    because we left the dst.expire value intact from the last update. So
    dst_set_expires won't touch dst.expires.

    Fix this by resetting dst.expires when clearing the RTF_EXPIRE flag.
    dst_set_expires checks for a zero expiration and updates the
    dst.expires.

    In the past this (not updating dst.expires) was necessary because
    dst.expire was placed in a union with the dst_entry *from reference
    and rt6_clean_expires did assign NULL to it. This split happend in
    ecd9883724b78cc72ed92c98bcb1a46c764fff21 ("ipv6: fix race condition
    regarding dst->expires and dst->from").

    Reported-by: Steinar H. Gunderson <sgunderson@bigfoot.com>
    Reported-by: Valentijn Sessink <valentyn@blub.net>
    Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
    Acked-by: Eric Dumazet <edumazet@google.com>
    Tested-by: Valentijn Sessink <valentyn@blub.net>
    Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    include/net/ip6_fib.h | 1 +
    1 file changed, 1 insertion(+)

    --- a/include/net/ip6_fib.h
    +++ b/include/net/ip6_fib.h
    @@ -165,6 +165,7 @@ static inline struct inet6_dev *ip6_dst_
    static inline void rt6_clean_expires(struct rt6_info *rt)
    {
    rt->rt6i_flags &= ~RTF_EXPIRES;
    + rt->dst.expires = 0;
    }

    static inline void rt6_set_expires(struct rt6_info *rt, unsigned long expires)



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