[PATCH 4.14 122/159] ip_gre: check packet length and mtu correctly in erspan tx

Greg Kroah-Hartman
2017-12-22T09:04:12Z

From: William Tu <u9012063@gmail.com>

[ Upstream commit f192970de860d3ab90aa9e2a22853201a57bde78 ]

Similarly to early patch for erspan_xmit(), the ARPHDR_ETHER device
is the length of the whole ether packet. So skb->len should subtract
the dev->hard_header_len.

Fixes: 1a66a836da63 ("gre: add collect_md mode to ERSPAN tunnel")
Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN")
Signed-off-by: William Tu <u9012063@gmail.com>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/ip_gre.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -579,8 +579,8 @@ static void erspan_fb_xmit(struct sk_buf
if (gre_handle_offloads(skb, false))
goto err_free_rt;

- if (skb->len > dev->mtu) {
- pskb_trim(skb, dev->mtu);
+ if (skb->len > dev->mtu + dev->hard_header_len) {
+ pskb_trim(skb, dev->mtu + dev->hard_header_len);
truncate = true;
}

@@ -731,8 +731,8 @@ static netdev_tx_t erspan_xmit(struct sk
if (skb_cow_head(skb, dev->needed_headroom))
goto free_skb;

- if (skb->len - dev->hard_header_len > dev->mtu) {
- pskb_trim(skb, dev->mtu);
+ if (skb->len > dev->mtu + dev->hard_header_len) {
+ pskb_trim(skb, dev->mtu + dev->hard_header_len);
truncate = true;
}