From: Willem de Bruijn <willemb@xxxxxxxxxx> commit 57031eb794906eea4e1c7b31dc1e2429c0af0c66 upstream. 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. [js] no virtio helpers in 3.12 Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx> Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Willy Tarreau <w@xxxxxx> --- net/packet/af_packet.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 4b1734a..9bff8a9 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2242,7 +2242,7 @@ static int packet_snd(struct socket *sock, int vnet_hdr_len; struct packet_sock *po = pkt_sk(sk); unsigned short gso_type = 0; - int hlen, tlen; + int hlen, tlen, linear; int extra_len = 0; /* @@ -2336,7 +2336,9 @@ static int packet_snd(struct socket *sock, err = -ENOBUFS; hlen = LL_RESERVED_SPACE(dev); tlen = dev->needed_tailroom; - skb = packet_alloc_skb(sk, hlen + tlen, hlen, len, vnet_hdr.hdr_len, + linear = 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; -- 2.8.0.rc2.1.gbe9624a