Re: [PATCH net-next] ipv6: fix access to non-linear packet in ndisc_fill_redirect_hdr_option()

[Eric Dumazet <eric.dumazet@gmail.com>]

On Fri, 2018-03-02 at 11:53 +0100, Lorenzo Bianconi wrote:
> Fix the following slab-out-of-bounds kasan report in
> ndisc_fill_redirect_hdr_option when the incoming ipv6 packet is not
> linear and the accessed data are not in the linear data region of orig_skb
> 

> Reported-by: Jianlin Shi <jishi@redhat.com>
> Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
> ---
>  net/ipv6/ndisc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
> index 0a19ce3a6f7f..afd8c15827cd 100644
> --- a/net/ipv6/ndisc.c
> +++ b/net/ipv6/ndisc.c
> @@ -1554,7 +1554,8 @@ static void ndisc_fill_redirect_hdr_option(struct sk_buff *skb,
>  	*(opt++) = (rd_len >> 3);
>  	opt += 6;
>  
> -	memcpy(opt, ipv6_hdr(orig_skb), rd_len - 8);
> +	skb_copy_bits(orig_skb, skb_network_offset(orig_skb), opt,
> +		      rd_len - 8);
>  }

Wow, nice catch !

Reviewed-by: Eric Dumazet <edumazet@google.com>