netdev - Re: [PATCH net-next 1/2] ipv6: do not set routes if disable

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Date:   Wed, 28 Mar 2018 13:12:20 -0600
From:   David Ahern <dsahern@...il.com>
To:     Lorenzo Bianconi <lorenzo.bianconi@...hat.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] ipv6: do not set routes if disable_ipv6 has
 been enabled

On 3/27/18 11:11 AM, Lorenzo Bianconi wrote:
> Do not allow to set ipv6 routes from userspace if disable_ipv6 has been
> enabled. The issue can be triggered using the following reproducer:
> 
> - sysctl net.ipv6.conf.all.disable_ipv6=1
> - ip -6 route add a:b:c:d::/64 dev em1
> - ip -6 route show
>   a:b:c:d::/64 dev em1 metric 1024 pref medium
> 
> Fix it checking disable_ipv6 value in ip6_route_info_create routine
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
> ---
>  net/ipv6/route.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 1d0eaa69874d..672fd7fdb037 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -2917,6 +2917,11 @@ static struct rt6_info *ip6_route_info_create(struct fib6_config *cfg,
>  	if (!dev)
>  		goto out;
>  
> +	if (idev->cnf.disable_ipv6) {
> +		err = -EACCES;

you need an extack message telling the user that IPv6 is disabled on the
nexthop device.

> +		goto out;
> +	}
> +
>  	if (!(dev->flags & IFF_UP)) {
>  		NL_SET_ERR_MSG(extack, "Nexthop device is not up");
>  		err = -ENETDOWN;
>