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Commit 57031eb7 authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

packet: round up linear to header len 



Link layer protocols may unconditionally pull headers, as Ethernet
does in eth_type_trans. Ensure that the entire link layer header
always lies in the skb linear segment. tpacket_snd has such a check.
Extend this to packet_snd.

Variable length link layer headers complicate the computation
somewhat. Here skb->len may be smaller than dev->hard_header_len.

Round up the linear length to be at least as long as the smallest of
the two.

Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 217e6fa2

net/packet/af_packet.c

+4 −3
Original line number Diff line number Diff line
@@ -2755,7 +2755,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) 
	struct virtio_net_hdr vnet_hdr = { 0 };

	int offset = 0;

	struct packet_sock *po = pkt_sk(sk);

	int hlen, tlen;

	int hlen, tlen, linear;

	int extra_len = 0;



	/*
@@ -2816,8 +2816,9 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) 
	err = -ENOBUFS;

	hlen = LL_RESERVED_SPACE(dev);

	tlen = dev->needed_tailroom;

	skb = packet_alloc_skb(sk, hlen + tlen, hlen, len,

			       __virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len),

	linear = __virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len);

	linear = max(linear, min_t(int, len, dev->hard_header_len));

	skb = packet_alloc_skb(sk, hlen + tlen, hlen, len, linear,

			       msg->msg_flags & MSG_DONTWAIT, &err);

	if (skb == NULL)

		goto out_unlock;