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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 6C0E8C43331 for ; Tue, 31 Mar 2020 14:13:31 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 27CD62078B for ; Tue, 31 Mar 2020 14:13:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Ilc9eR4q" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 27CD62078B 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 ([::1]:38720 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJHdy-0004ii-8H for qemu-devel@archiver.kernel.org; Tue, 31 Mar 2020 10:13:30 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48989) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJHd4-0003nV-OD for qemu-devel@nongnu.org; Tue, 31 Mar 2020 10:12:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jJHd3-0003KV-9a for qemu-devel@nongnu.org; Tue, 31 Mar 2020 10:12:34 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:27776 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jJHd3-0003Jh-5j for qemu-devel@nongnu.org; Tue, 31 Mar 2020 10:12:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585663952; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oufbEk1H6j3OE6EP5HvuQlhQOcnlItPwArlIgcuQCS4=; b=Ilc9eR4qUCU3EAcb5B5Xzvw6lnYssG5dP8d845XUhBSHVLz3czc9U4yOl2RyHwnrcxLSk2 beEcpytFrymL0n5/2lMorCJXwdyVSSOVTUxAghZxiP9vdriNI0Z5omVfnOQ9b/8Yfsst39 6Y/8kXIgxfM0iRsEfsRLFbvzfVmlHGw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-185-bMr3PTcTPFC8dZzBxk13Tw-1; Tue, 31 Mar 2020 10:12:18 -0400 X-MC-Unique: bMr3PTcTPFC8dZzBxk13Tw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EC133881295; Tue, 31 Mar 2020 14:12:16 +0000 (UTC) Received: from redhat.com (unknown [10.36.110.48]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DAA86608E7; Tue, 31 Mar 2020 14:12:08 +0000 (UTC) Date: Tue, 31 Mar 2020 15:12:05 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH-for-5.0 v2 1/4] Revert "prevent crash when executing guest-file-read with large count" Message-ID: <20200331141205.GI353752@redhat.com> References: <20200331140638.16464-1-philmd@redhat.com> <20200331140638.16464-2-philmd@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200331140638.16464-2-philmd@redhat.com> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: qemu-devel@nongnu.org, Michael Roth , Fakhri Zulkifli , Markus Armbruster , Sameeh Jubran , Basil Salman , Dietmar Maurer , "Dr . David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Mar 31, 2020 at 04:06:35PM +0200, Philippe Mathieu-Daud=C3=A9 wrote= : > By using g_try_malloc() instead of g_malloc() the qemu-guest-agent > Denial-of-Service attack referred in commit 807e2b6fce is reduced, > but still triggerable: As explained previously, I believe there is *no* denial of service attack here. The described scenario is just a user hurting themselves by intentionally telling QEMU not to limit the amount of data returned. >=20 > - bisect file size S until g_try_malloc(S) fails, > - use S - 1: > g_try_malloc(S - 1) succeeds, but g_new0() few lines later will > fail. >=20 > 346 buf =3D g_try_malloc0(count + 1); > 347 if (!buf) { > 348 error_setg(errp, > 349 "failed to allocate sufficient memory " > 350 "to complete the requested service"); > 351 return NULL; > 352 } > 353 is_ok =3D ReadFile(fh, buf, count, &read_count, NULL); > 354 if (!is_ok) { > 355 error_setg_win32(errp, GetLastError(), "failed to read file"= ); > 356 slog("guest-file-read failed, handle %" PRId64, handle); > 357 } else { > 358 buf[read_count] =3D 0; > 359 read_data =3D g_new0(GuestFileRead, 1); > ^^^^^^ >=20 > Instead we are going to put a low hard limit on 'count' in the next > commits. > This reverts commit 807e2b6fce022707418bc8f61c069d91c613b3d2. >=20 > Suggested-by: Daniel P. Berrang=C3=A9 > Signed-off-by: Philippe Mathieu-Daud=C3=A9 > --- > qga/commands-win32.c | 8 +------- > 1 file changed, 1 insertion(+), 7 deletions(-) >=20 > diff --git a/qga/commands-win32.c b/qga/commands-win32.c > index b49920e201..46cea7d1d9 100644 > --- a/qga/commands-win32.c > +++ b/qga/commands-win32.c > @@ -343,13 +343,7 @@ GuestFileRead *qmp_guest_file_read(int64_t handle, b= ool has_count, > } > =20 > fh =3D gfh->fh; > - buf =3D g_try_malloc0(count + 1); > - if (!buf) { > - error_setg(errp, > - "failed to allocate sufficient memory " > - "to complete the requested service"); > - return NULL; > - } > + buf =3D g_malloc0(count + 1); > is_ok =3D ReadFile(fh, buf, count, &read_count, NULL); > if (!is_ok) { > error_setg_win32(errp, GetLastError(), "failed to read file"); > --=20 > 2.21.1 >=20 Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberrange= :| |: https://libvirt.org -o- https://fstop138.berrange.com= :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange= :|