[PATCH 3.16 171/306] tty: limit terminal size to 4M chars

From: Ben Hutchings
Date: Wed Feb 15 2017 - 18:23:18 EST

3.16.40-rc1 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>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
drivers/tty/vt/vt.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -863,6 +863,8 @@ 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;