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    Subject[PATCH 4.4 65/74] net: qdisc_pkt_len_init() should be more robust
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Eric Dumazet <edumazet@google.com>


    [ Upstream commit 7c68d1a6b4db9012790af7ac0f0fdc0d2083422a ]

    Without proper validation of DODGY packets, we might very well
    feed qdisc_pkt_len_init() with invalid GSO packets.

    tcp_hdrlen() might access out-of-bound data, so let's use
    skb_header_pointer() and proper checks.

    Whole story is described in commit d0c081b49137 ("flow_dissector:
    properly cap thoff field")

    We have the goal of validating DODGY packets earlier in the stack,
    so we might very well revert this fix in the future.

    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Cc: Willem de Bruijn <willemb@google.com>
    Cc: Jason Wang <jasowang@redhat.com>
    Reported-by: syzbot+9da69ebac7dddd804552@syzkaller.appspotmail.com
    Acked-by: Jason Wang <jasowang@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/core/dev.c | 19 +++++++++++++++----
    1 file changed, 15 insertions(+), 4 deletions(-)

    --- a/net/core/dev.c
    +++ b/net/core/dev.c
    @@ -2889,10 +2889,21 @@ static void qdisc_pkt_len_init(struct sk
    hdr_len = skb_transport_header(skb) - skb_mac_header(skb);

    /* + transport layer */
    - if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
    - hdr_len += tcp_hdrlen(skb);
    - else
    - hdr_len += sizeof(struct udphdr);
    + if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) {
    + const struct tcphdr *th;
    + struct tcphdr _tcphdr;
    +
    + th = skb_header_pointer(skb, skb_transport_offset(skb),
    + sizeof(_tcphdr), &_tcphdr);
    + if (likely(th))
    + hdr_len += __tcp_hdrlen(th);
    + } else {
    + struct udphdr _udphdr;
    +
    + if (skb_header_pointer(skb, skb_transport_offset(skb),
    + sizeof(_udphdr), &_udphdr))
    + hdr_len += sizeof(struct udphdr);
    + }

    if (shinfo->gso_type & SKB_GSO_DODGY)
    gso_segs = DIV_ROUND_UP(skb->len - hdr_len,

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