vt_kdsetmode: extend console locking

vt_kdsetmode: extend console locking

Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit?id=60d69cb4e60de0067e5d8aecacd86dfe92a5384a
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2021-3753

commit 2287a51ba822384834dafc1c798453375d1107c7 upstream.

As per the long-suffering comment.

Reported-by: Minh Yuan <yuanmingbuaa@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Gbp-Pq: Topic bugfix/all
Gbp-Pq: Name vt_kdsetmode-extend-console-locking.patch