From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 16ED4C4363D for ; Thu, 24 Sep 2020 14:42:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD21F2311A for ; Thu, 24 Sep 2020 14:42:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728184AbgIXOmY convert rfc822-to-8bit (ORCPT ); Thu, 24 Sep 2020 10:42:24 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:57386 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727889AbgIXOmY (ORCPT ); Thu, 24 Sep 2020 10:42:24 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-263-piLz1VFuP7WR1Dja3TezJQ-1; Thu, 24 Sep 2020 15:42:19 +0100 X-MC-Unique: piLz1VFuP7WR1Dja3TezJQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Thu, 24 Sep 2020 15:42:18 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Thu, 24 Sep 2020 15:42:18 +0100 From: David Laight To: 'Greg Kroah-Hartman' , Peilin Ye , Daniel Vetter CC: Bartlomiej Zolnierkiewicz , Jiri Slaby , "dri-devel@lists.freedesktop.org" , "linux-fbdev@vger.kernel.org" , "linux-kernel-mentees@lists.linuxfoundation.org" , "syzkaller-bugs@googlegroups.com" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH 0/3] Prevent out-of-bounds access for built-in font data buffers Thread-Topic: [PATCH 0/3] Prevent out-of-bounds access for built-in font data buffers Thread-Index: AQHWknxPKqK+ilVBT0etUz37fvqXO6l33I9A Date: Thu, 24 Sep 2020 14:42:18 +0000 Message-ID: <394733ab6fae47488d078cb22f22a85b@AcuMS.aculab.com> References: <0000000000006b9e8d059952095e@google.com> <20200924140937.GA749208@kroah.com> In-Reply-To: <20200924140937.GA749208@kroah.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Thu, Sep 24, 2020 at 09:38:22AM -0400, Peilin Ye wrote: > > Hi all, > > > > syzbot has reported [1] a global out-of-bounds read issue in > > fbcon_get_font(). A malicious user may resize `vc_font.height` to a large > > value in vt_ioctl(), causing fbcon_get_font() to overflow our built-in > > font data buffers, declared in lib/fonts/font_*.c: ... > > (drivers/video/fbdev/core/fbcon.c) > > if (font->width <= 8) { > > j = vc->vc_font.height; > > + if (font->charcount * j > FNTSIZE(fontdata)) > > + return -EINVAL; Can that still go wrong because the multiply wraps? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)