Re: [PATCH -stable] netfilter: ipt_rpfilter: remove the nh_scope test in rpfilter_lookup_reverse

[Luis Henriques <luis.henriques@canonical.com>]

On Mon, Dec 14, 2015 at 01:17:14PM +0100, Pablo Neira Ayuso wrote:
> From: lucien <lucien.xin@gmail.com>
> 
> [ upstream commit cc4998febd567d1c671684abce5595344bd4e8b2 ]
> 
> --accept-local  option works for res.type == RTN_LOCAL, which should be
> from the local table, but there, the fib_info's nh->nh_scope =
> RT_SCOPE_NOWHERE ( > RT_SCOPE_HOST). in fib_create_info().
> 
> 	if (cfg->fc_scope == RT_SCOPE_HOST) {
> 		struct fib_nh *nh = fi->fib_nh;
> 
> 		/* Local address is added. */
> 		if (nhs != 1 || nh->nh_gw)
> 			goto err_inval;
> 		nh->nh_scope = RT_SCOPE_NOWHERE;   <===
> 		nh->nh_dev = dev_get_by_index(net, fi->fib_nh->nh_oif);
> 		err = -ENODEV;
> 		if (!nh->nh_dev)
> 			goto failure;
> 
> but in our rpfilter_lookup_reverse():
> 
> 	if (dev_match || flags & XT_RPFILTER_LOOSE)
> 		return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;
> 
> if nh->nh_scope > RT_SCOPE_HOST, it will fail. --accept-local option
> will never be passed.
> 
> it seems the test is bogus and can be removed to fix this issue.
> 
> 	if (dev_match || flags & XT_RPFILTER_LOOSE)
> 		return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;
> 
> ipv6 does not have this issue.
> 
> Cc: <stable@vger.kernel.org> # 3.14.x
> Cc: <stable@vger.kernel.org> # 3.18.x
> Cc: <stable@vger.kernel.org> # 4.1.x
> Cc: <stable@vger.kernel.org> # 4.2.x

Thanks, I'm queuing this one and the next 2 to the 3.16 kernel as well
(some of the other patches had already been included).

Cheers,
--
Luís


> Signed-off-by: Xin Long <lucien.xin@gmail.com>
> Acked-by: Florian Westphal <fw@strlen.de>
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> ---
>  net/ipv4/netfilter/ipt_rpfilter.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/net/ipv4/netfilter/ipt_rpfilter.c b/net/ipv4/netfilter/ipt_rpfilter.c
> index 8618fd1..c4ffc9d 100644
> --- a/net/ipv4/netfilter/ipt_rpfilter.c
> +++ b/net/ipv4/netfilter/ipt_rpfilter.c
> @@ -61,9 +61,7 @@ static bool rpfilter_lookup_reverse(struct flowi4 *fl4,
>  	if (FIB_RES_DEV(res) == dev)
>  		dev_match = true;
>  #endif
> -	if (dev_match || flags & XT_RPFILTER_LOOSE)
> -		return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;
> -	return dev_match;
> +	return dev_match || flags & XT_RPFILTER_LOOSE;
>  }
>  
>  static bool rpfilter_is_local(const struct sk_buff *skb)
> -- 
> 2.1.4
> 
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