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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 56E76C87FCE for ; Mon, 28 Jul 2025 09:05:12 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ugJmx-0007iX-JY; Mon, 28 Jul 2025 05:04:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ugJmv-0007f9-CE for qemu-devel@nongnu.org; Mon, 28 Jul 2025 05:04:53 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ugJmt-0007YG-0J for qemu-devel@nongnu.org; Mon, 28 Jul 2025 05:04:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753693489; 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=V5vcxWTU4e+4T7st/JfhiKpTGDipixuS68Sm21F5p/c=; b=dh07J5mWlwTkS7B/xMH9cN2mAzEUlVnbgZy9TMAN7MI6lrnVDfaZf7evFM7s/QZFh1pYFB rX0PxnEZ4N7a/KjYjXhDGHUGXzmZfThwMVndcTChyD/B36Fkj+c9le2hyihN7pmRxCPmiC 4mOAIG2ubhwdvHiLRAk9n7eILvC33EE= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-587-BAS_26nMNNm0JEMKBCjGtA-1; Mon, 28 Jul 2025 05:04:45 -0400 X-MC-Unique: BAS_26nMNNm0JEMKBCjGtA-1 X-Mimecast-MFC-AGG-ID: BAS_26nMNNm0JEMKBCjGtA_1753693484 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2B1211956095; Mon, 28 Jul 2025 09:04:43 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.32]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A0FA51800242; Mon, 28 Jul 2025 09:04:39 +0000 (UTC) Date: Mon, 28 Jul 2025 10:04:36 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Michael Tokarev Cc: qemu-devel@nongnu.org, Paolo Bonzini , Peter Xu , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Fabiano Rosas Subject: Re: [PATCH 0/4] migration: workaround GNUTLS live migration crashes Message-ID: References: <20250718150514.2635338-1-berrange@redhat.com> <9b37d573-1783-4b0e-9b16-e08a10824aa9@tls.msk.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <9b37d573-1783-4b0e-9b16-e08a10824aa9@tls.msk.ru> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=-1, RCVD_IN_MSPIKE_WL=-0.01, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Sat, Jul 26, 2025 at 09:24:10AM +0300, Michael Tokarev wrote: > On 18.07.2025 18:05, Daniel P. Berrangé wrote: > > TL:DR: GNUTLS is liable to crash QEMU when live migration is run > > with TLS enabled and a return path channel is present, if approx > > 64 GB of data is transferred. This is easily triggered in a 16 GB > > VM with 4 CPUs, by running 'stress-ng --vm 4 --vm-bytes 80%' to > > prevent convergance until 64 GB of RAM has been copied. Then > > triggering post-copy switchover, or removing the stress workload > > to allow completion, will crash it. > > > > The only live migration scenario that should avoid this danger > > is multifd, since the high volume data transfers are handled in > > dedicated TCP connections which are unidirectional. The main > > bi-directionl TCP connection is only for co-ordination purposes > > > > This patch implements a workaround that will prevent future QEMU > > versions from triggering the crash. > > > > The only way to avoid the crash with *existing* running QEMU > > processes is to change the TLS cipher priority string to avoid > > use of AES with TLS 1.3. This can be done with the 'priority' > > field in the 'tls-creds-x509' object.eg > > > > -object tls-creds-x509,id=tls0,priority=NORMAL:-AES-256-GCM:-AES-128-GCM:-AES-128-CCM > > > > which should force the use of CHACHA20-POLY1305 which does not > > require TLS re-keying after 16 million sent records (64 GB of > > migration data). > > > > https://gitlab.com/qemu-project/qemu/-/issues/1937 > > > > On RHEL/Fedora distros you can also use the system wide crypto > > priorities to override this from the migration *target* host > > by creating /etc/crypto-policies/local.d/gnutls-qemu.config > > containing > > > > QEMU=NONE:+ECDHE-RSA:+ECDHE-ECDSA:+RSA:+DHE-RSA:+GROUP-X25519:+GROUP-X448:+GROUP-SECP256R1:+GROUP-SECP384R1:+GROUP-SECP521R1:+GROUP-FF > > > > and running 'update-crypto-policies'. I recommend the QEMU > > level 'tls-creds-x509' workaround though, which new libvirt > > patches can soon do: > > > > https://lists.libvirt.org/archives/list/devel@lists.libvirt.org/thread/LX5KMIUFZSP5DPUXKJDFYBZI5TIE3E5N/ > > > > Daniel P. Berrangé (4): > > crypto: implement workaround for GNUTLS thread safety problems > > io: add support for activating TLS thread safety workaround > > migration: activate TLS thread safety workaround > > crypto: add tracing & warning about GNUTLS countermeasures > > > > crypto/tlssession.c | 99 +++++++++++++++++++++++++++++++++-- > > crypto/trace-events | 2 + > > include/crypto/tlssession.h | 14 +++++ > > include/io/channel.h | 1 + > > io/channel-tls.c | 5 ++ > > meson.build | 9 ++++ > > meson_options.txt | 2 + > > migration/tls.c | 9 ++++ > > scripts/meson-buildoptions.sh | 5 ++ > > 9 files changed, 143 insertions(+), 3 deletions(-) > > Being a large(ish) change, but it looks like this patch set is a good > candidate for qemu-stable series, at least for 10.0.x. What do you > think? Yeah, given broken gnutls is everywhere, I'd take it to any stable tree where it is reasonably easy to do a clean backport. With regards, Daniel -- |: 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 :|