vt_kdsetmode: extend console locking

BugLink: https://bugs.launchpad.net/bugs/1944610
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index af75a01ef6321766e84875513dd896753545607a..7b80921e5e01372450d6213644ff2644b7e7aee7 100644 (file)
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -246,6 +246,8 @@ int vt_waitactive(int n)
  *
  * XXX It should at least call into the driver, fbdev's definitely need to
  * restore their engine state. --BenH
+ *
+ * Called with the console lock held.
  */
 static int vt_kdsetmode(struct vc_data *vc, unsigned long mode)
 {
@@ -262,7 +264,6 @@ static int vt_kdsetmode(struct vc_data *vc, unsigned long mode)
                return -EINVAL;
        }
 
-       /* FIXME: this needs the console lock extending */
        if (vc->vc_mode == mode)
                return 0;
 
@@ -271,12 +272,10 @@ static int vt_kdsetmode(struct vc_data *vc, unsigned long mode)
                return 0;
 
        /* explicitly blank/unblank the screen if switching modes */
-       console_lock();
        if (mode == KD_TEXT)
                do_unblank_screen(1);
        else
                do_blank_screen(1);
-       console_unlock();
 
        return 0;
 }
@@ -378,7 +377,10 @@ static int vt_k_ioctl(struct tty_struct *tty, unsigned int cmd,
                if (!perm)
                        return -EPERM;
 
-               return vt_kdsetmode(vc, arg);
+               console_lock();
+               ret = vt_kdsetmode(vc, arg);
+               console_unlock();
+               return ret;
 
        case KDGETMODE:
                return put_user(vc->vc_mode, (int __user *)arg);