[patch added to 3.12-stable] tty: limit terminal size to 4M chars

From: Jiri Slaby
Date: Tue Nov 22 2016 - 17:40:49 EST

From: Dmitry Vyukov <dvyukov@xxxxxxxxxx>

This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.


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: Jiri Slaby <jslaby@xxxxxxx>
drivers/tty/vt/vt.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index d52e653076f4..60ce423c6364 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -863,6 +863,8 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
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;