Re: [PATCH net] packet: reset network header if packet shorter than ll reserved space

[David Miller]

From: Willem de Bruijn 
Date: Wed, 11 Jul 2018 12:00:45 -0400

> From: Willem de Bruijn 
> 
> If variable length link layer headers result in a packet shorter
> than dev->hard_header_len, reset the network header offset. Else
> skb->mac_len may exceed skb->len after skb_mac_reset_len.
> 
> packet_sendmsg_spkt already has similar logic.
> 
> Fixes: b84bbaf7a6c8 ("packet: in packet_snd start writing at link layer 
> allocation")
> Signed-off-by: Willem de Bruijn 

Applied and queued up for -stable.

[PATCH net] packet: reset network header if packet shorter than ll reserved space

[Willem de Bruijn]

From: Willem de Bruijn 

If variable length link layer headers result in a packet shorter
than dev->hard_header_len, reset the network header offset. Else
skb->mac_len may exceed skb->len after skb_mac_reset_len.

packet_sendmsg_spkt already has similar logic.

Fixes: b84bbaf7a6c8 ("packet: in packet_snd start writing at link layer 
allocation")
Signed-off-by: Willem de Bruijn 
---
 net/packet/af_packet.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 57634bc3da74..9b27d0cd766d 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2878,6 +2878,8 @@ static int packet_snd(struct socket *sock, struct msghdr 
*msg, size_t len)
goto out_free;
} else if (reserve) {
skb_reserve(skb, -reserve);
+   if (len < reserve)
+   skb_reset_network_header(skb);
}
 
/* Returns -EFAULT on error */
-- 
2.18.0.203.gfac676dfb9-goog