netdev - Re: [PATCH net-next] tun: Do SIOCGSKNS out of rtnl

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Date:   Wed, 9 May 2018 15:18:14 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>, davem@...emloft.net,
        edumazet@...gle.com, mst@...hat.com, brouer@...hat.com,
        peterpenkov96@...il.com, sd@...asysnail.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tun: Do SIOCGSKNS out of rtnl_lock()



On 2018年05月09日 00:21, Kirill Tkhai wrote:
> Since net ns of tun device is assigned on the device creation,
> and it never changes, we do not need to use any lock to get it
> from alive tun.
>
> Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
> ---
>   drivers/net/tun.c |   18 +++++++-----------
>   1 file changed, 7 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index d3c04ab9752a..44d4f3d25350 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2850,10 +2850,10 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
>   			    unsigned long arg, int ifreq_len)
>   {
>   	struct tun_file *tfile = file->private_data;
> +	struct net *net = sock_net(&tfile->sk);
>   	struct tun_struct *tun;
>   	void __user* argp = (void __user*)arg;
>   	struct ifreq ifr;
> -	struct net *net;
>   	kuid_t owner;
>   	kgid_t group;
>   	int sndbuf;
> @@ -2877,14 +2877,18 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
>   		 */
>   		return put_user(IFF_TUN | IFF_TAP | TUN_FEATURES,
>   				(unsigned int __user*)argp);
> -	} else if (cmd == TUNSETQUEUE)
> +	} else if (cmd == TUNSETQUEUE) {
>   		return tun_set_queue(file, &ifr);
> +	} else if (cmd == SIOCGSKNS) {

Not for this patch, reusing socket ioctl cmd is probably not good though 
they were probably not intersected (see ioctl-number.txt). We probably 
need to introduce TUN specific ioctls for SIOCGSKNS and SIOCGIFHWADDR 
and warn for socket ones.

Thanks

> +		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
> +			return -EPERM;
> +		return open_related_ns(&net->ns, get_net_ns);
> +	}
>   
>   	ret = 0;
>   	rtnl_lock();
>   
>   	tun = tun_get(tfile);
> -	net = sock_net(&tfile->sk);
>   	if (cmd == TUNSETIFF) {
>   		ret = -EEXIST;
>   		if (tun)
> @@ -2914,14 +2918,6 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
>   		tfile->ifindex = ifindex;
>   		goto unlock;
>   	}
> -	if (cmd == SIOCGSKNS) {
> -		ret = -EPERM;
> -		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
> -			goto unlock;
> -
> -		ret = open_related_ns(&net->ns, get_net_ns);
> -		goto unlock;
> -	}
>   
>   	ret = -EBADFD;
>   	if (!tun)
>