ACK: [SRU][Bionic][PATCH 1/1] xfrm: Verify MAC header exists before overwriting eth_hdr(skb)->h_proto

[Stefan Bader]

On 11.10.2018 21:49, Joseph Salisbury wrote:
> From: Yossi Kuperman <yossiku at mellanox.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1795653
> 
> Artem Savkov reported that commit 5efec5c655dd leads to a packet loss under
> IPSec configuration. It appears that his setup consists of a TUN device,
> which does not have a MAC header.
> 
> Make sure MAC header exists.
> 
> Note: TUN device sets a MAC header pointer, although it does not have one.
> 
> Fixes: 5efec5c655dd ("xfrm: Fix eth_hdr(skb)->h_proto to reflect inner IP version")
> Reported-by: Artem Savkov <artem.savkov at gmail.com>
> Tested-by: Artem Savkov <artem.savkov at gmail.com>
> Signed-off-by: Yossi Kuperman <yossiku at mellanox.com>
> Signed-off-by: Steffen Klassert <steffen.klassert at secunet.com>
> (cherry picked from commit 87cdf3148b11d46382dbce2754ae7036aba96380)
> Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>  net/ipv4/xfrm4_mode_tunnel.c | 3 ++-
>  net/ipv6/xfrm6_mode_tunnel.c | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/xfrm4_mode_tunnel.c b/net/ipv4/xfrm4_mode_tunnel.c
> index 20ca486..acdde9d 100644
> --- a/net/ipv4/xfrm4_mode_tunnel.c
> +++ b/net/ipv4/xfrm4_mode_tunnel.c
> @@ -92,7 +92,8 @@ static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
>  
>  	skb_reset_network_header(skb);
>  	skb_mac_header_rebuild(skb);
> -	eth_hdr(skb)->h_proto = skb->protocol;
> +	if (skb->mac_len)
> +		eth_hdr(skb)->h_proto = skb->protocol;
>  
>  	err = 0;
>  
> diff --git a/net/ipv6/xfrm6_mode_tunnel.c b/net/ipv6/xfrm6_mode_tunnel.c
> index dc93002..1ff2cff 100644
> --- a/net/ipv6/xfrm6_mode_tunnel.c
> +++ b/net/ipv6/xfrm6_mode_tunnel.c
> @@ -92,7 +92,8 @@ static int xfrm6_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
>  
>  	skb_reset_network_header(skb);
>  	skb_mac_header_rebuild(skb);
> -	eth_hdr(skb)->h_proto = skb->protocol;
> +	if (skb->mac_len)
> +		eth_hdr(skb)->h_proto = skb->protocol;
>  
>  	err = 0;
>  
> 


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