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 B7D00D62060 for ; Tue, 19 Nov 2024 10:04:38 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tDL5B-0004vX-Qk; Tue, 19 Nov 2024 05:03:41 -0500 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 1tDL58-0004v6-L1 for qemu-devel@nongnu.org; Tue, 19 Nov 2024 05:03:39 -0500 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 1tDL55-00073x-Sh for qemu-devel@nongnu.org; Tue, 19 Nov 2024 05:03:38 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1732010614; 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:in-reply-to:in-reply-to: references:references; bh=+2WfRg8Dh13SOa3rwlqa6ItDiMr6SUZcHXcYex2L5Hk=; b=UjxO5bthXaq7Ac8yeuBt8xfm9pO9J59VJLx9dObIjDt0rotcvyB3wMV2UFI3rxd6Z3V7ma SRbslsl6N9rFnPgcsL4XtPZtplAzPnEFu5x+0p0qSuY0yh1GC1uEi4eeRujS9T0xuv+c0i b2T4NonGEcd/TKJGs4gI9dtJSmbImsk= Received: from mx-prod-mc-01.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-389-jTw4AIadOzirXuGeupyBbg-1; Tue, 19 Nov 2024 05:03:30 -0500 X-MC-Unique: jTw4AIadOzirXuGeupyBbg-1 X-Mimecast-MFC-AGG-ID: jTw4AIadOzirXuGeupyBbg Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9402919560AF; Tue, 19 Nov 2024 10:03:29 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.110]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3FBCE1956086; Tue, 19 Nov 2024 10:03:25 +0000 (UTC) Date: Tue, 19 Nov 2024 10:03:22 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: qemu-devel@nongnu.org, Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Fabiano Rosas , Juraj Marcin , Markus Armbruster , Eduardo Habkost , Peter Maydell , =?utf-8?Q?C=C3=A9dric?= Le Goater , Paolo Bonzini Subject: Re: [PATCH 5/5] qom: Make container_get() strict to always walk or return container Message-ID: References: <20241118221330.3480246-1-peterx@redhat.com> <20241118221330.3480246-6-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241118221330.3480246-6-peterx@redhat.com> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.142, 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_H2=-0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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: 2.1.29 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 Mon, Nov 18, 2024 at 05:13:30PM -0500, Peter Xu wrote: > When used incorrectly, container_get() can silently create containers even > if the caller may not intend to do so. Add a rich document describing the > helper, as container_get() should only be used in path lookups. > > Add one object_dynamic_cast() check to make sure whatever objects the > helper walks will be a container object (including the one to be returned). > It is a programming error otherwise, hence assert that. > > It may make container_get() tiny slower than before, but the hope is the > change is neglictable, as object_class_dynamic_cast() has a fast path just > for similar leaf use case. > > Link: https://lore.kernel.org/r/87pln6ds8q.fsf@pond.sub.org > Suggested-by: Markus Armbruster > Signed-off-by: Peter Xu > --- > qom/container.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/qom/container.c b/qom/container.c > index cfec92a944..ff6e35f837 100644 > --- a/qom/container.c > +++ b/qom/container.c > @@ -24,6 +24,20 @@ static void container_register_types(void) > type_register_static(&container_info); > } > > +/** > + * container_get(): Get the container object under specific path > + * > + * @root: The root path object to start walking from. When starting from > + * root, one can pass in object_get_root(). > + * @path: The sub-path to lookup, must be an non-empty string starts with "/". > + * > + * Returns: The container object specified by @path. > + * > + * NOTE: the function may impplicitly create internal containers when the > + * whole path is not yet created. It's the caller's responsibility to make > + * sure the path specified is always used as object containers, rather than > + * any other type of objects. > + */ The docs are a welcome addition, but at the same time the docs won't get read most of the time. With this in mind, IMHO, it is a conceptually *terrible* design for us to have a method called "get" which magically *creates* stuff as a side-effect of its calling. We'd be well served by fixing that design problem. If I look in the code at what calls we have to container_get, and more specifically what "path" values we pass, there are not actually that many: /objects /chardevs /unattached /machine /peripheral /peripheral-anon /backend /dr-connector Ignoring the last one, those other 7 containers are things we expect to exist in *every* system emulator. Second, every single one of them is a single level deep. IOW, the for() loop in container_get is effectively pointless. We can fix this by having a single method: void container_create_builtin(Object *root) which creates the 7 built-in standard containers we expect everywhere, with open coded object_new + add_child calls. Then all current users of container_get() can switch over to object_resolve_path, and container_get() can be eliminated. The 'dr-connector' creation can just be open-coded using object_new() in the spapr code. > Object *container_get(Object *root, const char *path) > { > Object *obj, *child; > @@ -31,6 +45,7 @@ Object *container_get(Object *root, const char *path) > int i; > > parts = g_strsplit(path, "/", 0); > + /* "path" must be an non-empty string starting with "/" */ > assert(parts != NULL && parts[0] != NULL && !parts[0][0]); > obj = root; > > @@ -40,6 +55,12 @@ Object *container_get(Object *root, const char *path) > child = object_new(TYPE_CONTAINER); > object_property_add_child(obj, parts[i], child); > object_unref(child); > + } else { > + /* > + * Each object within the path must be a container object > + * itself, including the object to be returned. > + */ > + assert(object_dynamic_cast(child, TYPE_CONTAINER)); > } > } > > -- > 2.45.0 > 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 :|