vt: hold console_sem across sysfs operations

Hold console sem while creating/destroying sysfs files.  Serialisation is
so far done by BKL held in tty release_dev and chrdev_open, but no other
locks are held in open path.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Aristeu Rozanski <aris@ruivo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/vt.c

@@ -2749,8 +2749,8 @@ static int con_open(struct tty_struct *tty, struct file *filp)
 				tty->termios->c_iflag |= IUTF8;
 			else
 				tty->termios->c_iflag &= ~IUTF8;
-			release_console_sem();
 			vcs_make_sysfs(tty);
+			release_console_sem();
 			return ret;
 		}
 	}
@@ -2775,8 +2775,8 @@ static void con_close(struct tty_struct *tty, struct file *filp)
 		if (vc)
 			vc->vc_tty = NULL;
 		tty->driver_data = NULL;
-		release_console_sem();
 		vcs_remove_sysfs(tty);
+		release_console_sem();
 		mutex_unlock(&tty_mutex);
 		/*
 		 * tty_mutex is released, but we still hold BKL, so there is