From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:49773) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hE5mu-0003Ue-Ef for qemu-devel@nongnu.org; Wed, 10 Apr 2019 01:28:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hE5mt-0004GP-G7 for qemu-devel@nongnu.org; Wed, 10 Apr 2019 01:28:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35340) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hE5mt-0004G8-7W for qemu-devel@nongnu.org; Wed, 10 Apr 2019 01:28:43 -0400 From: Markus Armbruster References: <20190409174018.25798-1-armbru@redhat.com> Date: Wed, 10 Apr 2019 07:28:36 +0200 In-Reply-To: ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Tue, 9 Apr 2019 20:59:55 +0200") Message-ID: <874l764eez.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH for-4.0-maybe] device_tree: Fix integer overflowing in load_device_tree() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: qemu-devel@nongnu.org, peter.maydell@linaro.org, alistair.francis@wdc.com, slp@redhat.com, david@gibson.dropbear.id.au Philippe Mathieu-Daud=C3=A9 writes: > On 4/9/19 7:40 PM, Markus Armbruster wrote: >> If the value of get_image_size() exceeds INT_MAX / 2 - 10000, the >> computation of @dt_size overflows to a negative number, which then >> gets converted to a very large size_t for g_malloc0() and >> load_image_size(). In the (fortunately improbable) case g_malloc0() >> succeeds and load_image_size() survives, we'd assign the negative >> number to *sizep. What that would do to the callers I can't say, but >> it's unlikely to be good. >>=20 >> Fix by rejecting images whose size would overflow. >>=20 >> Signed-off-by: Markus Armbruster >> --- >> device_tree.c | 4 ++++ >> 1 file changed, 4 insertions(+) >>=20 >> diff --git a/device_tree.c b/device_tree.c >> index 296278e12a..f8b46b3c73 100644 >> --- a/device_tree.c >> +++ b/device_tree.c >> @@ -84,6 +84,10 @@ void *load_device_tree(const char *filename_path, int= *sizep) >> filename_path); >> goto fail; >> } >> + if (dt_size > INT_MAX / 2 - 10000) { > > We should avoid magic number duplication. > That said, this patch looks safe. > > Reviewed-by: Philippe Mathieu-Daud=C3=A9 Thanks! > BTW how did you figure that out? Downstream handling of upstream commit da885fe1ee8 led me to the function. I spotted dt_size =3D get_image_size(filename_path). Experience has taught me to check the left hand side's type. Bad. Then I saw how dt_size gets increased. Worse. >> + error_report("Device tree file '%s' is too large", filename_pat= h); >> + goto fail; >> + } >>=20=20 >> /* Expand to 2x size to give enough room for manipulation. */ >> dt_size +=3D 10000; >>=20 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 3D460C10F11 for ; Wed, 10 Apr 2019 05:29:34 +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 F2E2B20850 for ; Wed, 10 Apr 2019 05:29:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F2E2B20850 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]:53772 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hE5nh-0003mM-8f for qemu-devel@archiver.kernel.org; Wed, 10 Apr 2019 01:29:33 -0400 Received: from eggs.gnu.org ([209.51.188.92]:49773) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hE5mu-0003Ue-Ef for qemu-devel@nongnu.org; Wed, 10 Apr 2019 01:28:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hE5mt-0004GP-G7 for qemu-devel@nongnu.org; Wed, 10 Apr 2019 01:28:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35340) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hE5mt-0004G8-7W for qemu-devel@nongnu.org; Wed, 10 Apr 2019 01:28:43 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 25F07CD01D; Wed, 10 Apr 2019 05:28:42 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-116.ams2.redhat.com [10.36.116.116]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CF6BA5D71E; Wed, 10 Apr 2019 05:28:37 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 589391138648; Wed, 10 Apr 2019 07:28:36 +0200 (CEST) From: Markus Armbruster To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= References: <20190409174018.25798-1-armbru@redhat.com> Date: Wed, 10 Apr 2019 07:28:36 +0200 In-Reply-To: ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Tue, 9 Apr 2019 20:59:55 +0200") Message-ID: <874l764eez.fsf@dusky.pond.sub.org> 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 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 10 Apr 2019 05:28:42 +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 for-4.0-maybe] device_tree: Fix integer overflowing in load_device_tree() 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@linaro.org, alistair.francis@wdc.com, qemu-devel@nongnu.org, slp@redhat.com, david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190410052836.401QOMRTVfGG_gcVO9AUhfAXf1g6XhQSmG_3ySZo7vc@z> Philippe Mathieu-Daud=C3=A9 writes: > On 4/9/19 7:40 PM, Markus Armbruster wrote: >> If the value of get_image_size() exceeds INT_MAX / 2 - 10000, the >> computation of @dt_size overflows to a negative number, which then >> gets converted to a very large size_t for g_malloc0() and >> load_image_size(). In the (fortunately improbable) case g_malloc0() >> succeeds and load_image_size() survives, we'd assign the negative >> number to *sizep. What that would do to the callers I can't say, but >> it's unlikely to be good. >>=20 >> Fix by rejecting images whose size would overflow. >>=20 >> Signed-off-by: Markus Armbruster >> --- >> device_tree.c | 4 ++++ >> 1 file changed, 4 insertions(+) >>=20 >> diff --git a/device_tree.c b/device_tree.c >> index 296278e12a..f8b46b3c73 100644 >> --- a/device_tree.c >> +++ b/device_tree.c >> @@ -84,6 +84,10 @@ void *load_device_tree(const char *filename_path, int= *sizep) >> filename_path); >> goto fail; >> } >> + if (dt_size > INT_MAX / 2 - 10000) { > > We should avoid magic number duplication. > That said, this patch looks safe. > > Reviewed-by: Philippe Mathieu-Daud=C3=A9 Thanks! > BTW how did you figure that out? Downstream handling of upstream commit da885fe1ee8 led me to the function. I spotted dt_size =3D get_image_size(filename_path). Experience has taught me to check the left hand side's type. Bad. Then I saw how dt_size gets increased. Worse. >> + error_report("Device tree file '%s' is too large", filename_pat= h); >> + goto fail; >> + } >>=20=20 >> /* Expand to 2x size to give enough room for manipulation. */ >> dt_size +=3D 10000; >>=20