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    Subject[PATCH 4.3 17/71] packet: fix tpacket_snd max frame len
    Date
    4.3-stable review patch.  If anyone has any objections, please let me know.

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

    From: Daniel Borkmann <daniel@iogearbox.net>

    [ Upstream commit 5cfb4c8d05b4409c4044cb9c05b19705c1d9818b ]

    Since it's introduction in commit 69e3c75f4d54 ("net: TX_RING and
    packet mmap"), TX_RING could be used from SOCK_DGRAM and SOCK_RAW
    side. When used with SOCK_DGRAM only, the size_max > dev->mtu +
    reserve check should have reserve as 0, but currently, this is
    unconditionally set (in it's original form as dev->hard_header_len).

    I think this is not correct since tpacket_fill_skb() would then
    take dev->mtu and dev->hard_header_len into account for SOCK_DGRAM,
    the extra VLAN_HLEN could be possible in both cases. Presumably, the
    reserve code was copied from packet_snd(), but later on missed the
    check. Make it similar as we have it in packet_snd().

    Fixes: 69e3c75f4d54 ("net: TX_RING and packet mmap")
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    Acked-by: Willem de Bruijn <willemb@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/packet/af_packet.c | 9 +++++----
    1 file changed, 5 insertions(+), 4 deletions(-)

    --- a/net/packet/af_packet.c
    +++ b/net/packet/af_packet.c
    @@ -2510,12 +2510,13 @@ static int tpacket_snd(struct packet_soc
    if (unlikely(!(dev->flags & IFF_UP)))
    goto out_put;

    - reserve = dev->hard_header_len + VLAN_HLEN;
    + if (po->sk.sk_socket->type == SOCK_RAW)
    + reserve = dev->hard_header_len;
    size_max = po->tx_ring.frame_size
    - (po->tp_hdrlen - sizeof(struct sockaddr_ll));

    - if (size_max > dev->mtu + reserve)
    - size_max = dev->mtu + reserve;
    + if (size_max > dev->mtu + reserve + VLAN_HLEN)
    + size_max = dev->mtu + reserve + VLAN_HLEN;

    do {
    ph = packet_current_frame(po, &po->tx_ring,
    @@ -2542,7 +2543,7 @@ static int tpacket_snd(struct packet_soc
    tp_len = tpacket_fill_skb(po, skb, ph, dev, size_max, proto,
    addr, hlen);
    if (likely(tp_len >= 0) &&
    - tp_len > dev->mtu + dev->hard_header_len &&
    + tp_len > dev->mtu + reserve &&
    !packet_extra_vlan_len_allowed(dev, skb))
    tp_len = -EMSGSIZE;




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