4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Willem de Bruijn <willemb@xxxxxxxxxx> [ Upstream commit 57031eb794906eea4e1c7b31dc1e2429c0af0c66 ] 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@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: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/packet/af_packet.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2637,7 +2637,7 @@ static int packet_snd(struct socket *soc 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; ssize_t n; @@ -2741,8 +2741,9 @@ static int packet_snd(struct socket *soc 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;