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 BB857CCF9E3 for ; Fri, 24 Oct 2025 13:41:27 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vCI2k-0000rQ-K9; Fri, 24 Oct 2025 09:41:22 -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 1vCI2h-0000nM-5u for qemu-devel@nongnu.org; Fri, 24 Oct 2025 09:41:19 -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 1vCI2e-0000FN-BN for qemu-devel@nongnu.org; Fri, 24 Oct 2025 09:41:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761313274; h=from:from: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=JQ8uVIxocZv5A1dzBFS8FmytxEHoj/uCugF1QlAGDbc=; b=MUdc/jDnJjn8ctf/hqE4+JwsA3zc/Vng31jT0RCoFPpTXT67Nv5+Uq7QszURriYL0GbhUF NFOE4bSXWznGLTe9zPsOg/L79RgtaiSNWjlH8e0Z4B+tmQ22xYA+BZ4CjuJqSuisdS5qfM YhDI1NFu365RZQwTf6lFC54NPIw6iJM= Received: from mx-prod-mc-03.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-14-lXwG8sTIMlOR4UpzDK0eWA-1; Fri, 24 Oct 2025 09:41:11 -0400 X-MC-Unique: lXwG8sTIMlOR4UpzDK0eWA-1 X-Mimecast-MFC-AGG-ID: lXwG8sTIMlOR4UpzDK0eWA_1761313270 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2C03A19540E3; Fri, 24 Oct 2025 13:41:10 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.24]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D2E3B1800353; Fri, 24 Oct 2025 13:41:09 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 6901B21E6A27; Fri, 24 Oct 2025 15:41:07 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= 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 In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Fri, 24 Oct 2025 12:27:23 +0100") References: <20251024092821.82220-1-guobin@linux.alibaba.com> <87o6pw1rfn.fsf@pond.sub.org> Date: Fri, 24 Oct 2025 15:41:07 +0200 Message-ID: <874irozabw.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniel P. Berrang=C3=A9 writes: > On Fri, Oct 24, 2025 at 01:15:40PM +0200, Markus Armbruster wrote: >> Bin Guo writes: >>=20 >> > 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 i= s enabled"); >> > if (migrate_add_blocker(&kvm_nv_migration_blocker, errp)) { >> > - error_free(kvm_nv_migration_blocker); >> > return; >> > } >> >=20=20 >> > 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 =3D migrate_add_blocker(&sev_mig_blocker, &local_err); >> > if (local_err) { >> > error_report_err(local_err); >> > - error_free(sev_mig_blocker); >> > exit(1); >> > } >> > } >>=20 >> 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. It's quite a sight, isn't it? I'll give it a quick Friday afternoon try.