Subject: Re: [PATCH nf-next 1/6] netfilter: bridge: call pskb_may_pull in br_nf_check_hbh_len

From: Simon Horman <[email-masked]>
Date: Mon, 6 Mar 2023 16:52:41 +0100

On Fri, Mar 03, 2023 at 07:12:37PM -0500, Xin Long wrote:
> When checking Hop-by-hop option header, if the option data is in
> nonlinear area, it should do pskb_may_pull instead of discarding
> the skb as a bad IPv6 packet.
> 
> Signed-off-by: Xin Long <[email-masked]>

Reviewed-by: Simon Horman <[email-masked]>

> ---
>  net/bridge/br_netfilter_ipv6.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/net/bridge/br_netfilter_ipv6.c b/net/bridge/br_netfilter_ipv6.c
> index 6b07f30675bb..5cd3e4c35123 100644
> --- a/net/bridge/br_netfilter_ipv6.c
> +++ b/net/bridge/br_netfilter_ipv6.c
> @@ -45,14 +45,18 @@
>   */
>  static int br_nf_check_hbh_len(struct sk_buff *skb)
>  {
> -	unsigned char *raw = (u8 *)(ipv6_hdr(skb) + 1);
> +	int len, off = sizeof(struct ipv6hdr);
> +	unsigned char *nh;
>  	u32 pkt_len;
> -	const unsigned char *nh = skb_network_header(skb);
> -	int off = raw - nh;
> -	int len = (raw[1] + 1) << 3;
>  
> -	if ((raw + len) - skb->data > skb_headlen(skb))
> +	if (!pskb_may_pull(skb, off + 8))
>  		goto bad;
> +	nh = (u8 *)(ipv6_hdr(skb) + 1);

nit: if you need so spin a v2 perhaps it would be worth
     considering reconciling the type of nh (unsigned char *)
     with the type of the cast above (u8 *).

> +	len = (nh[1] + 1) << 3;
> +
> +	if (!pskb_may_pull(skb, off + len))
> +		goto bad;
> +	nh = skb_network_header(skb);
>  
>  	off += 2;
>  	len -= 2;
> -- 
> 2.39.1
>