From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:39763) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hGTxJ-0007Tn-M5 for qemu-devel@nongnu.org; Tue, 16 Apr 2019 15:41:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hGTxI-0000Dh-3m for qemu-devel@nongnu.org; Tue, 16 Apr 2019 15:41:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35078) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hGTxF-00009Q-BY for qemu-devel@nongnu.org; Tue, 16 Apr 2019 15:41:19 -0400 From: Bandan Das References: <20190415154503.6758-1-berrange@redhat.com> <20190415154503.6758-3-berrange@redhat.com> Date: Tue, 16 Apr 2019 15:41:09 -0400 In-Reply-To: <20190415154503.6758-3-berrange@redhat.com> ("Daniel P. \=\?utf-8\?Q\?Berrang\=C3\=A9\=22's\?\= message of "Mon, 15 Apr 2019 16:45:02 +0100") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH 2/3] usb-mtp: fix bounds check for guest provided filename List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. =?utf-8?Q?Berrang=C3=A9?=" Cc: qemu-devel@nongnu.org, Peter Maydell , Thomas Huth , Greg Kurz , Gerd Hoffmann Daniel P. Berrang=C3=A9 writes: > The ObjectInfo struct has a variable length array containing the UTF-16 > encoded filename. The number of characters of trailing data is given by > the 'length' field in the struct and this must be validated against the > size of the data packet received from the guest. > > Since the data is UTF-16, we must convert the byte count we have to a > character count before validating. This must take care to truncate if > a malicious guest sent an odd number of bytes. > > Signed-off-by: Daniel P. Berrang=C3=A9 > --- > hw/usb/dev-mtp.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/hw/usb/dev-mtp.c b/hw/usb/dev-mtp.c > index 838cd74da6..6b7d1296e4 100644 > --- a/hw/usb/dev-mtp.c > +++ b/hw/usb/dev-mtp.c > @@ -1699,12 +1699,19 @@ static void usb_mtp_write_metadata(MTPState *s, u= int64_t dlen) > MTPObject *o; > MTPObject *p =3D usb_mtp_object_lookup(s, s->dataset.parent_handle); > uint32_t next_handle =3D s->next_handle; > + size_t filename_chars =3D dlen - offsetof(ObjectInfo, filename); > + > + /* > + * filename is utf-16. We're intentionally doing > + * integer division to truncate if malicious guest > + * sent an odd number of bytes. > + */ > + filename_chars /=3D 2; >=20=20 > assert(!s->write_pending); > assert(p !=3D NULL); >=20=20 > - filename =3D utf16_to_str(MIN(dataset->length, > - dlen - offsetof(ObjectInfo, filename)), > + filename =3D utf16_to_str(MIN(dataset->length, filename_chars), > dataset->filename); >=20=20 > if (strchr(filename, '/')) { Reviewed-by: Bandan Das 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=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham 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 CDFD6C10F13 for ; Tue, 16 Apr 2019 19:42:09 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A638D20821 for ; Tue, 16 Apr 2019 19:42:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A638D20821 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:41878 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hGTy4-0007lu-Kg for qemu-devel@archiver.kernel.org; Tue, 16 Apr 2019 15:42:08 -0400 Received: from eggs.gnu.org ([209.51.188.92]:39763) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hGTxJ-0007Tn-M5 for qemu-devel@nongnu.org; Tue, 16 Apr 2019 15:41:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hGTxI-0000Dh-3m for qemu-devel@nongnu.org; Tue, 16 Apr 2019 15:41:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35078) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hGTxF-00009Q-BY for qemu-devel@nongnu.org; Tue, 16 Apr 2019 15:41:19 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A19C83092641; Tue, 16 Apr 2019 19:41:13 +0000 (UTC) Received: from gigantic.usersys.redhat.com (helium.bos.redhat.com [10.18.17.132]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D38B219C67; Tue, 16 Apr 2019 19:41:10 +0000 (UTC) From: Bandan Das To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= References: <20190415154503.6758-1-berrange@redhat.com> <20190415154503.6758-3-berrange@redhat.com> Date: Tue, 16 Apr 2019 15:41:09 -0400 In-Reply-To: <20190415154503.6758-3-berrange@redhat.com> ("Daniel P. \=\?utf-8\?Q\?Berrang\=C3\=A9\=22's\?\= message of "Mon, 15 Apr 2019 16:45:02 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Tue, 16 Apr 2019 19:41:13 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 2/3] usb-mtp: fix bounds check for guest provided filename X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Thomas Huth , Gerd Hoffmann , qemu-devel@nongnu.org, Greg Kurz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190416194109.V_OCeHFXm9Y1Fo-1frk4GJFM7FAI0ICaZcZgysfV8pM@z> Daniel P. Berrang=C3=A9 writes: > The ObjectInfo struct has a variable length array containing the UTF-16 > encoded filename. The number of characters of trailing data is given by > the 'length' field in the struct and this must be validated against the > size of the data packet received from the guest. > > Since the data is UTF-16, we must convert the byte count we have to a > character count before validating. This must take care to truncate if > a malicious guest sent an odd number of bytes. > > Signed-off-by: Daniel P. Berrang=C3=A9 > --- > hw/usb/dev-mtp.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/hw/usb/dev-mtp.c b/hw/usb/dev-mtp.c > index 838cd74da6..6b7d1296e4 100644 > --- a/hw/usb/dev-mtp.c > +++ b/hw/usb/dev-mtp.c > @@ -1699,12 +1699,19 @@ static void usb_mtp_write_metadata(MTPState *s, u= int64_t dlen) > MTPObject *o; > MTPObject *p =3D usb_mtp_object_lookup(s, s->dataset.parent_handle); > uint32_t next_handle =3D s->next_handle; > + size_t filename_chars =3D dlen - offsetof(ObjectInfo, filename); > + > + /* > + * filename is utf-16. We're intentionally doing > + * integer division to truncate if malicious guest > + * sent an odd number of bytes. > + */ > + filename_chars /=3D 2; >=20=20 > assert(!s->write_pending); > assert(p !=3D NULL); >=20=20 > - filename =3D utf16_to_str(MIN(dataset->length, > - dlen - offsetof(ObjectInfo, filename)), > + filename =3D utf16_to_str(MIN(dataset->length, filename_chars), > dataset->filename); >=20=20 > if (strchr(filename, '/')) { Reviewed-by: Bandan Das