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packet: fix tpacket_snd max frame len

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Since it's introduction in commit 69e3c75f4d ("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: 69e3c75f4d ("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>
This commit is contained in:
Daniel Borkmann 2015-11-11 23:25:44 +01:00 committed by David S. Miller
parent c72219b75f
commit 5cfb4c8d05
1 changed files with 5 additions and 4 deletions
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9
net/packet/af_packet.c
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@ -2510,12 +2510,13 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
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_sock *po, struct msghdr *msg)
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;