Re: [PATCH v2] gso: fix payload length when gso_size is zero

["Duyck, Alexander H" <alexander.h.duyck@intel.com>]

On Fri, 2017-10-06 at 19:02 +0300, Alexey Kodanev wrote:
> When gso_size reset to zero for the tail segment in skb_segment(), later
> in ipv6_gso_segment(), __skb_udp_tunnel_segment() and gre_gso_segment()
> we will get incorrect results (payload length, pcsum) for that segment.
> inet_gso_segment() already has a check for gso_size before calculating
> payload.
> 
> The issue was found with LTP vxlan & gre tests over ixgbe NIC.
> 
> Fixes: 07b26c9454a2 ("gso: Support partial splitting at the frag_list pointer")
> Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>

Acked-by: Alexander Duyck <alexander.h.duyck@intel.com>

> ---
> v2: also added skb_is_gso to gre_gso_segment() and __skb_udp_tunnel_segment()
> 
>  net/ipv4/gre_offload.c | 2 +-
>  net/ipv4/udp_offload.c | 2 +-
>  net/ipv6/ip6_offload.c | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
> index d5cac99..8c72034 100644
> --- a/net/ipv4/gre_offload.c
> +++ b/net/ipv4/gre_offload.c
> @@ -98,7 +98,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
>  		greh = (struct gre_base_hdr *)skb_transport_header(skb);
>  		pcsum = (__sum16 *)(greh + 1);
>  
> -		if (gso_partial) {
> +		if (gso_partial && skb_is_gso(skb)) {
>  			unsigned int partial_adj;
>  
>  			/* Adjust checksum to account for the fact that
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 0932c85..6401574 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -122,7 +122,7 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
>  		 * will be using a length value equal to only one MSS sized
>  		 * segment instead of the entire frame.
>  		 */
> -		if (gso_partial) {
> +		if (gso_partial && skb_is_gso(skb)) {
>  			uh->len = htons(skb_shinfo(skb)->gso_size +
>  					SKB_GSO_CB(skb)->data_offset +
>  					skb->head - (unsigned char *)uh);
> diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> index cdb3728..4a87f94 100644
> --- a/net/ipv6/ip6_offload.c
> +++ b/net/ipv6/ip6_offload.c
> @@ -105,7 +105,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
>  
>  	for (skb = segs; skb; skb = skb->next) {
>  		ipv6h = (struct ipv6hdr *)(skb_mac_header(skb) + nhoff);
> -		if (gso_partial)
> +		if (gso_partial && skb_is_gso(skb))
>  			payload_len = skb_shinfo(skb)->gso_size +
>  				      SKB_GSO_CB(skb)->data_offset +
>  				      skb->head - (unsigned char *)(ipv6h + 1);