[PATCH 4.4 08/10] vt_kdsetmode: extend console locking

From: Greg Kroah-Hartman
Date: Wed Sep 01 2021 - 08:27:03 EST


From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

commit 2287a51ba822384834dafc1c798453375d1107c7 upstream.

As per the long-suffering comment.

Reported-by: Minh Yuan <yuanmingbuaa@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Jiri Slaby <jirislaby@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/vt/vt_ioctl.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -487,16 +487,19 @@ int vt_ioctl(struct tty_struct *tty,
ret = -EINVAL;
goto out;
}
- /* FIXME: this needs the console lock extending */
- if (vc->vc_mode == (unsigned char) arg)
+ console_lock();
+ if (vc->vc_mode == (unsigned char) arg) {
+ console_unlock();
break;
+ }
vc->vc_mode = (unsigned char) arg;
- if (console != fg_console)
+ if (console != fg_console) {
+ console_unlock();
break;
+ }
/*
* explicitly blank/unblank the screen if switching modes
*/
- console_lock();
if (arg == KD_TEXT)
do_unblank_screen(1);
else