Re: [PATCH v2] net: don't unconditionally copy_from_user a struct ifreq for socket ioctls

[Jakub Kicinski]

On Thu, 26 Aug 2021 12:46:01 -0700 Peter Collingbourne wrote:
> @@ -3306,6 +3308,8 @@ static int compat_ifr_data_ioctl(struct net *net, unsigned int cmd,
>  	struct ifreq ifreq;
>  	u32 data32;
>  
> +	if (!is_socket_ioctl_cmd(cmd))
> +		return -ENOTTY;
>  	if (copy_from_user(ifreq.ifr_name, u_ifreq32->ifr_name, IFNAMSIZ))
>  		return -EFAULT;
>  	if (get_user(data32, &u_ifreq32->ifr_data))

Hi Peter, when resolving the net -> net-next merge conflict I couldn't
figure out why this chunk is needed. It seems all callers of
compat_ifr_data_ioctl() already made sure it's a socket IOCTL.
Please double check my resolution (tip of net-next) and if this is
indeed unnecessary perhaps send a cleanup? Thanks!