Commit 5cfb4c8d authored Nov 11, 2015 by Daniel Borkmann Committed by David S. Miller Nov 15, 2015

packet: fix tpacket_snd max frame len



Since it's introduction in commit 69e3c75f ("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: 69e3c75f ("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>

parent c72219b7

net/packet/af_packet.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -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;