[PATCH 4.4 17/20] packet: round up linear to header len

From: Greg Kroah-Hartman
Date: Thu Feb 16 2017 - 13:09:02 EST

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;