Re: [PATCH net] fou, fou6: do not assume linear skbs

[Stefano Brivio]

On Fri, 11 Jan 2019 04:55:52 -0800
Eric Dumazet <eduma...@google.com> wrote:

> Both gue_err() and gue6_err() incorrectly assume
> linear skbs. Fix them to use pskb_may_pull().

Thanks for fixing this! I stupidly didn't suspect we could get
non-linear skbs there. Just two things:

> +++ b/net/ipv4/fou.c
> @@ -1020,10 +1020,11 @@ static int gue_err(struct sk_buff *skb, u32 info)
>  {
>       int transport_offset = skb_transport_offset(skb);
>       struct guehdr *guehdr;
> -     size_t optlen;
> +     size_t len, optlen;
>       int ret;
>  
> -     if (skb->len < sizeof(struct udphdr) + sizeof(struct guehdr))
> +     len = sizeof(struct udphdr) + sizeof(struct guehdr);
> +     if (!pskb_may_pull(skb, len))
>               return -EINVAL;
>  
>       guehdr = (struct guehdr *)&udp_hdr(skb)[1];
> @@ -1058,6 +1059,10 @@ static int gue_err(struct sk_buff *skb, u32 info)
>  
>       optlen = guehdr->hlen << 2;
>  
> +     if (!pskb_may_pull(skb, len + optlen)
                                             ^ ) missing

> +             return -EINVAL;
> +
> +     guehdr = (struct guehdr *)&udp_hdr(skb)[1];
>       if (validate_gue_flags(guehdr, optlen))
>               return -EINVAL;
>  
> diff --git a/net/ipv6/fou6.c b/net/ipv6/fou6.c
> index 
> 7da7bf3b7fe3953eeb60addfffd6687c4da582c4..320413af4890641e7199d7d7102e7d8c2794d557
>  100644
> --- a/net/ipv6/fou6.c
> +++ b/net/ipv6/fou6.c
> @@ -90,10 +90,11 @@ static int gue6_err(struct sk_buff *skb, struct 
> inet6_skb_parm *opt,
>  {
>       int transport_offset = skb_transport_offset(skb);
>       struct guehdr *guehdr;
> -     size_t optlen;
> +     size_t len, optlen;
>       int ret;
>  
> -     if (skb->len < sizeof(struct udphdr) + sizeof(struct guehdr))
> +     len = sizeof(struct udphdr) + sizeof(struct guehdr);
> +     if (!pskb_may_pull(skb, len))
>               return -EINVAL;
>  
>       guehdr = (struct guehdr *)&udp_hdr(skb)[1];
> @@ -128,6 +129,10 @@ static int gue6_err(struct sk_buff *skb, struct 
> inet6_skb_parm *opt,
>  
>       optlen = guehdr->hlen << 2;
>  
> +     if (!pskb_may_pull(skb, len + optlen)
                                             ^ ) missing

> +             return -EINVAL;
> +
> +     guehdr = (struct guehdr *)&udp_hdr(skb)[1];
>       if (validate_gue_flags(guehdr, optlen))
>               return -EINVAL;
>  

-- 
Stefano