From patchwork Mon Oct 26 13:51:18 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 302029 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=-9.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED 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 45B54C4363A for ; Mon, 26 Oct 2020 13:56:57 +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 C852A22242 for ; Mon, 26 Oct 2020 13:56:56 +0000 (UTC) Authentication-Results: mail.kernel.org; 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Mon, 26 Oct 2020 13:51:33 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 25B756EF78; Mon, 26 Oct 2020 13:51:33 +0000 (UTC) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 04/17] hw/core/qdev-clock: add a reference on aliased clocks Date: Mon, 26 Oct 2020 09:51:18 -0400 Message-Id: <20201026135131.3006712-5-pbonzini@redhat.com> In-Reply-To: <20201026135131.3006712-1-pbonzini@redhat.com> References: <20201026135131.3006712-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=63.128.21.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/25 21:03:19 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Luc Michel , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Luc Michel When aliasing a clock with the qdev_alias_clock() function, a new link property is created on the device aliasing the clock. The link points to the aliased clock and use the OBJ_PROP_LINK_STRONG flag. This property is read only since it does not provide a check callback for modifications. The object_property_add_link() documentation stats that with OBJ_PROP_LINK_STRONG properties, the linked object reference count get decremented when the property is deleted. But it is _not_ incremented on creation (object_property_add_link() does not actually know the link). This commit increments the reference count on the aliased clock to ensure the aliased clock stays alive during the property lifetime, and to avoid a double-free memory error when the property gets deleted. Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Luc Michel Message-Id: <20201020091024.320381-1-luc@lmichel.fr> Signed-off-by: Paolo Bonzini --- hw/core/qdev-clock.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/hw/core/qdev-clock.c b/hw/core/qdev-clock.c index 6a9a340d0f..eb05f2a13c 100644 --- a/hw/core/qdev-clock.c +++ b/hw/core/qdev-clock.c @@ -61,6 +61,14 @@ static NamedClockList *qdev_init_clocklist(DeviceState *dev, const char *name, object_get_typename(OBJECT(clk)), (Object **) &ncl->clock, NULL, OBJ_PROP_LINK_STRONG); + /* + * Since the link property has the OBJ_PROP_LINK_STRONG flag, the clk + * object reference count gets decremented on property deletion. + * However object_property_add_link does not increment it since it + * doesn't know the linked object. Increment it here to ensure the + * aliased clock stays alive during this device life-time. + */ + object_ref(OBJECT(clk)); } ncl->clock = clk;