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 746F5CCD1AB for ; Fri, 24 Oct 2025 11:27:54 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vCFxQ-0001U7-1Q; Fri, 24 Oct 2025 07:27:44 -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 1vCFxK-0001Tf-3n for qemu-devel@nongnu.org; Fri, 24 Oct 2025 07:27:38 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vCFxG-0003ZF-Lm for qemu-devel@nongnu.org; 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Fri, 24 Oct 2025 11:27:30 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.2]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5982730002D7; Fri, 24 Oct 2025 11:27:26 +0000 (UTC) Date: Fri, 24 Oct 2025 12:27:23 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Cc: Bin Guo , qemu-devel@nongnu.org, peterx@redhat.com, farosas@suse.de Subject: Re: [PATCH] migration: Don't free the reason after calling migrate_add_blocker Message-ID: References: <20251024092821.82220-1-guobin@linux.alibaba.com> <87o6pw1rfn.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87o6pw1rfn.fsf@pond.sub.org> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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 Fri, Oct 24, 2025 at 01:15:40PM +0200, Markus Armbruster wrote: > Bin Guo writes: > > > Signed-off-by: Bin Guo > > --- > > hw/intc/arm_gicv3_kvm.c | 1 - > > target/i386/sev.c | 1 - > > 2 files changed, 2 deletions(-) > > > > diff --git a/hw/intc/arm_gicv3_kvm.c b/hw/intc/arm_gicv3_kvm.c > > index 66b0dddfd4..6f311e37ef 100644 > > --- a/hw/intc/arm_gicv3_kvm.c > > +++ b/hw/intc/arm_gicv3_kvm.c > > @@ -841,7 +841,6 @@ static void kvm_arm_gicv3_realize(DeviceState *dev, Error **errp) > > error_setg(&kvm_nv_migration_blocker, > > "Live migration disabled because KVM nested virt is enabled"); > > if (migrate_add_blocker(&kvm_nv_migration_blocker, errp)) { > > - error_free(kvm_nv_migration_blocker); > > return; > > } > > > > diff --git a/target/i386/sev.c b/target/i386/sev.c > > index 1057b8ab2c..fd2dada013 100644 > > --- a/target/i386/sev.c > > +++ b/target/i386/sev.c > > @@ -1661,7 +1661,6 @@ sev_snp_launch_finish(SevCommonState *sev_common) > > ret = migrate_add_blocker(&sev_mig_blocker, &local_err); > > if (local_err) { > > error_report_err(local_err); > > - error_free(sev_mig_blocker); > > exit(1); > > } > > } > > Does this fix use-after-free bugs? I don't think so, because when migrate_add_blocker() returns error, the Error for the blocker will have been propagated into the errp parameter, and then set to NULL. So these two error_free calls should be a no-op. But wow, the migrate_add_blocker API design is unpleasant with its pair of "Error **" parameters - it is practically designed to maximise confusion & surprise. 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 :|