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    Subject[PATCH 48/98] netfilter: xt_TCPOPTSTRIP: don't use tcp_hdr()
    Date
    3.5.7.17 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Pablo Neira Ayuso <pablo@netfilter.org>

    commit ed82c437320c48a4032492f4a55a7e2c934158b6 upstream.

    In (bc6bcb5 netfilter: xt_TCPOPTSTRIP: fix possible mangling beyond
    packet boundary), the use of tcp_hdr was introduced. However, we
    cannot assume that skb->transport_header is set for non-local packets.

    Cc: Florian Westphal <fw@strlen.de>
    Reported-by: Phil Oester <kernel@linuxace.com>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    net/netfilter/xt_TCPOPTSTRIP.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    diff --git a/net/netfilter/xt_TCPOPTSTRIP.c b/net/netfilter/xt_TCPOPTSTRIP.c
    index 1eb1a44..b68fa19 100644
    --- a/net/netfilter/xt_TCPOPTSTRIP.c
    +++ b/net/netfilter/xt_TCPOPTSTRIP.c
    @@ -48,11 +48,13 @@ tcpoptstrip_mangle_packet(struct sk_buff *skb,
    return NF_DROP;

    len = skb->len - tcphoff;
    - if (len < (int)sizeof(struct tcphdr) ||
    - tcp_hdr(skb)->doff * 4 > len)
    + if (len < (int)sizeof(struct tcphdr))
    return NF_DROP;

    tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
    + if (tcph->doff * 4 > len)
    + return NF_DROP;
    +
    opt = (u_int8_t *)tcph;

    /*
    --
    1.8.1.2


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