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

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: William Tu <u9012...@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 <u9012...@gmail.com>
Cc: Xin Long <lucien....@gmail.com>
Cc: David Laight <david.lai...@aculab.com>
Reviewed-by: Xin Long <lucien....@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Sasha Levin <alexander.le...@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gre...@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;
        }