[PATCH 2/2] vt: add permission check for KDSKBMETA ioctl

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Joshua Rogers <linux@joshua.hu>

KDSKBMETA modifies keyboard meta mode but lacks the !perm check that all
other keyboard setter ioctls in vt_k_ioctl() enforce, allowing a process
to change meta mode on a non-controlling console without authorization.

Assisted-by: AISLE:Snapshot
Cc: stable <stable@kernel.org>
Signed-off-by: Joshua Rogers <linux@joshua.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/vt/vt_ioctl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 28993a3d0acb..deb3b3f93461 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -406,6 +406,8 @@ static int vt_k_ioctl(struct tty_struct *tty, unsigned int cmd,
 	/* this could be folded into KDSKBMODE, but for compatibility
 	   reasons it is not so easy to fold KDGKBMETA into KDGKBMODE */
 	case KDSKBMETA:
+		if (!perm)
+			return -EPERM;
 		return vt_do_kdskbmeta(console, arg);
 
 	case KDGKBMETA:

-- 
2.55.0