netdev - Re: [PATCH net 1/3] net/ipv6: fix addrconf_sysctl_addr_gen

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Message-ID: <3c53aeaf-912f-8921-c9df-40f2caa1747a@gmail.com>
Date:   Fri, 6 Jul 2018 08:42:01 -0600
From:   David Ahern <dsahern@...il.com>
To:     Sabrina Dubroca <sd@...asysnail.net>, netdev@...r.kernel.org
Cc:     Jiri Pirko <jiri@...nulli.us>,
        Felix Jia <felix.jia@...iedtelesis.co.nz>
Subject: Re: [PATCH net 1/3] net/ipv6: fix addrconf_sysctl_addr_gen_mode

On 7/6/18 7:49 AM, Sabrina Dubroca wrote:
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 91580c62bb86..e9ba53d2a147 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -5892,32 +5892,31 @@ static int addrconf_sysctl_addr_gen_mode(struct ctl_table *ctl, int write,
>  					 loff_t *ppos)
>  {
>  	int ret = 0;
> -	int new_val;
> +	u32 new_val;
>  	struct inet6_dev *idev = (struct inet6_dev *)ctl->extra1;
>  	struct net *net = (struct net *)ctl->extra2;
> +	struct ctl_table tmp = {
> +		.data = &new_val,
> +		.maxlen = sizeof(new_val),
> +		.mode = ctl->mode,
> +	};
>  
>  	if (!rtnl_trylock())
>  		return restart_syscall();
>  
> -	ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
> +	new_val = *((u32 *)ctl->data);
>  
> -	if (write) {
> -		new_val = *((int *)ctl->data);
> +	ret = proc_douintvec(&tmp, write, buffer, lenp, ppos);
> +	if (ret != 0)
> +		goto out;
>  
> +	if (write) {
>  		if (check_addr_gen_mode(new_val) < 0) {
>  			ret = -EINVAL;
>  			goto out;
>  		}
>  
> -		/* request for default */
> -		if (&net->ipv6.devconf_dflt->addr_gen_mode == ctl->data) {
> -			ipv6_devconf_dflt.addr_gen_mode = new_val;

updating the template is wrong, but you still need to update the
namespace's default value for new devices.

also, if you are fixing this it would be good to handle the change to
'all' as well and update all existing devices.

> -
> -		/* request for individual net device */
> -		} else {
> -			if (!idev)
> -				goto out;
> -
> +		if (idev) {
>  			if (check_stable_privacy(idev, net, new_val) < 0) {
>  				ret = -EINVAL;
>  				goto out;
> @@ -5928,6 +5927,8 @@ static int addrconf_sysctl_addr_gen_mode(struct ctl_table *ctl, int write,
>  				addrconf_dev_config(idev->dev);
>  			}
>  		}
> +
> +		*((u32 *)ctl->data) = new_val;
>  	}
>  
>  out:
>