packet: round up linear to header len (57031eb7) · Commits · 戴 / test

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:

Dmitry Vyukov <dvyukov@google.com> Signed-off-by:

Willem de Bruijn <willemb@google.com> Acked-by:

Eric Dumazet <edumazet@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

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;

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