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

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Date:   Tue, 22 Nov 2016 23:40:06 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Peter Hurley <peter@...leysoftware.com>,
        linux-kernel@...r.kernel.org, syzkaller@...glegroups.com,
        Jiri Slaby <jslaby@...e.cz>
Subject: [patch added to 3.12-stable] tty: limit terminal size to 4M chars

From: Dmitry Vyukov <dvyukov@...gle.com>

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@...gle.com>
CC: David Rientjes <rientjes@...gle.com>
Cc: One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jslaby@...e.com>
Cc: Peter Hurley <peter@...leysoftware.com>
Cc: linux-kernel@...r.kernel.org
Cc: syzkaller@...glegroups.com
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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;
-- 
2.10.2