From: Dmitry Vyukov <dvyukov@google.com>
Date: Fri, 14 Oct 2016 13:18:28 +0000 (+0200)
Subject: tty: limit terminal size to 4M chars
X-Git-Tag: firefly_0821_release~176^2~4^2~19^2~39
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=00877d139396a19d8fdd5ccfd5ec627f64ac052b;p=firefly-linux-kernel-4.4.55.git

tty: limit terminal size to 4M chars

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@google.com>
CC: David Rientjes <rientjes@google.com>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: linux-kernel@vger.kernel.org
Cc: syzkaller@googlegroups.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 43c02004356d..004aa0fab4d8 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -872,6 +872,8 @@ 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;