tty: n_gsm: require CAP_NET_ADMIN to attach N_GSM0710 ldisc

stable inclusion
from stable-v4.19.315
commit 7d303dee473ba3529d75b63491e9963342107bed
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9S26U
CVE: CVE-2023-52880

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7d303dee473ba3529d75b63491e9963342107bed



--------------------------------

commit 67c37756 upstream.

Any unprivileged user can attach N_GSM0710 ldisc, but it requires
CAP_NET_ADMIN to create a GSM network anyway.

Require initial namespace CAP_NET_ADMIN to do that.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Link: https://lore.kernel.org/r/20230731185942.279611-1-cascardo@canonical.com


Cc: Salvatore Bonaccorso <carnil@debian.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Xiang Yang <xiangyang3@huawei.com>