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

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Message-Id: <20161109102847.686203083@linuxfoundation.org>
Date:   Wed,  9 Nov 2016 11:45:46 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
        Jiri Slaby <jslaby@...e.com>,
        Peter Hurley <peter@...leysoftware.com>,
        syzkaller@...glegroups.com
Subject: [PATCH 4.8 063/138] tty: limit terminal size to 4M chars

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

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

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

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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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;