Re: net/dev: fix information leak to userspace

[Cong Wang]

On Sun, Mar 21, 2021 at 9:34 AM Pavel Machek <pavel@xxxxxxx> wrote:
>
> dev_get_mac_address() does not always initialize whole
> structure. Unfortunately, other code copies such structure to
> userspace, leaking information. Fix it.

Well, most callers already initialize it with a memset() or copy_from_user(),
for example, __tun_chr_ioctl():

        if (cmd == TUNSETIFF || cmd == TUNSETQUEUE ||
            (_IOC_TYPE(cmd) == SOCK_IOC_TYPE && cmd != SIOCGSKNS)) {
                if (copy_from_user(&ifr, argp, ifreq_len))
                        return -EFAULT;
        } else {
                memset(&ifr, 0, sizeof(ifr));
        }

Except tap_ioctl(), but we can just initialize 'sa' there instead of doing
it in dev_get_mac_address().

Thanks.