[PATCH 4.8 063/138] tty: limit terminal size to 4M chars

[Greg Kroah-Hartman]

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dmitry Vyukov <dvyukov@xxxxxxxxxx>

commit 32b2921e6a7461fe63b71217067a6cf4bddb132f upstream.

Size of kmalloc() in vc_do_resize() is controlled by user.
Too large kmalloc() size triggers WARNING message on console.
Put a reasonable upper bound on terminal size to prevent WARNINGs.

Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
CC: David Rientjes <rientjes@xxxxxxxxxx>
Cc: One Thousand Gnomes <gnomes@xxxxxxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxxx>
Cc: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: syzkaller@xxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/tty/vt/vt.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -870,6 +870,8 @@ static int vc_do_resize(struct tty_struc
 	if (new_cols == vc->vc_cols && new_rows == vc->vc_rows)
 		return 0;
 
+	if (new_screen_size > (4 << 20))
+		return -EINVAL;
 	newscreen = kmalloc(new_screen_size, GFP_USER);
 	if (!newscreen)
 		return -ENOMEM;