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    Subject[PATCH 50/75] ipv6: ip6_sk_dst_check() must not assume ipv6 dst
    Date
    3.8.13.6 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit a963a37d384d71ad43b3e9e79d68d42fbe0901f3 ]

    It's possible to use AF_INET6 sockets and to connect to an IPv4
    destination. After this, socket dst cache is a pointer to a rtable,
    not rt6_info.

    ip6_sk_dst_check() should check the socket dst cache is IPv6, or else
    various corruptions/crashes can happen.

    Dave Jones can reproduce immediate crash with
    trinity -q -l off -n -c sendmsg -c connect

    With help from Hannes Frederic Sowa

    Reported-by: Dave Jones <davej@redhat.com>
    Reported-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    net/ipv6/ip6_output.c | 8 +++++++-
    1 file changed, 7 insertions(+), 1 deletion(-)

    diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
    index 2adff32..978e4a3 100644
    --- a/net/ipv6/ip6_output.c
    +++ b/net/ipv6/ip6_output.c
    @@ -843,11 +843,17 @@ static struct dst_entry *ip6_sk_dst_check(struct sock *sk,
    const struct flowi6 *fl6)
    {
    struct ipv6_pinfo *np = inet6_sk(sk);
    - struct rt6_info *rt = (struct rt6_info *)dst;
    + struct rt6_info *rt;

    if (!dst)
    goto out;

    + if (dst->ops->family != AF_INET6) {
    + dst_release(dst);
    + return NULL;
    + }
    +
    + rt = (struct rt6_info *)dst;
    /* Yes, checking route validity in not connected
    * case is not very simple. Take into account,
    * that we do not support routing by source, TOS,
    --
    1.8.1.2


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