From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.90_1) id 1rcoPq-0006o7-42 for mharc-qemu-trivial@gnu.org; Wed, 21 Feb 2024 10:21:46 -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 1rcoMQ-0001hh-DD for qemu-trivial@nongnu.org; Wed, 21 Feb 2024 10:18:18 -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 1rckqL-0005qh-Pn for qemu-trivial@nongnu.org; Wed, 21 Feb 2024 06:32:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1708515173; 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: in-reply-to:in-reply-to:references:references; bh=F/PfOV0rUULq7uskiVKCK2tU5oYWzUOp5ZIfBHAUq90=; b=XrMtiGzKrM7Ck+roZh6qn/6YexsuMvZHJb1PhO+BH/oZr2X/V5x3iWAkTitOm5Ms82LWg8 UmRcVZnMSmtVhuC/hvMnXSKGDzeK2FjPg+wvPRP3/WDq7OGziaJplOEdzdTVISiA1OLqEq AHa9+7rnFL1DmnySWF4hQlWnkrzGC0U= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-203-N-lm8KnBN5mXUv1hGgdvnA-1; Wed, 21 Feb 2024 06:32:45 -0500 X-MC-Unique: N-lm8KnBN5mXUv1hGgdvnA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id DC7633C40B50; Wed, 21 Feb 2024 11:32:44 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.55]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B41B5C185C1; Wed, 21 Feb 2024 11:32:44 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id B052021E66D5; Wed, 21 Feb 2024 12:32:43 +0100 (CET) From: Markus Armbruster To: Zhao Liu Cc: Jonathan Cameron , Fan Ni , Laurent Vivier , Alistair Francis , "Edgar E . Iglesias" , Peter Maydell , "Michael S . Tsirkin" , Marcel Apfelbaum , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org, qemu-arm@nongnu.org, qemu-trivial@nongnu.org, Zhao Liu Subject: Re: [PATCH 2/6] hw/display/macfb: Fix missing ERRP_GUARD() in macfb_nubus_realize() In-Reply-To: <20240221094317.994454-3-zhao1.liu@linux.intel.com> (Zhao Liu's message of "Wed, 21 Feb 2024 17:43:13 +0800") References: <20240221094317.994454-1-zhao1.liu@linux.intel.com> <20240221094317.994454-3-zhao1.liu@linux.intel.com> Date: Wed, 21 Feb 2024 12:32:43 +0100 Message-ID: <874je2vyqs.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@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=-0.05, 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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Feb 2024 15:18:26 -0000 Zhao Liu writes: > From: Zhao Liu > > As the comment in qapi/error, dereferencing @errp requires > ERRP_GUARD(): > > * = Why, when and how to use ERRP_GUARD() = > * > * Without ERRP_GUARD(), use of the @errp parameter is restricted: > * - It must not be dereferenced, because it may be null. > * - It should not be passed to error_prepend() or > * error_append_hint(), because that doesn't work with &error_fatal. > * ERRP_GUARD() lifts these restrictions. > * > * To use ERRP_GUARD(), add it right at the beginning of the function. > * @errp can then be used without worrying about the argument being > * NULL or &error_fatal. > * > * Using it when it's not needed is safe, but please avoid cluttering > * the source with useless code. > > Currently, since macfb_nubus_realize() - as a DeviceClass.realize() > method - doesn't get the NULL errp parameter, it doesn't trigger the > dereference issue. > > To follow the requirement of errp, add missing ERRP_GUARD() in > macfb_nubus_realize(). > > Suggested-by: Markus Armbruster > Signed-off-by: Zhao Liu > --- > Suggested by credit: > Markus: Referred his explanation about ERRP_GUARD(). > --- > hw/display/macfb.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/hw/display/macfb.c b/hw/display/macfb.c > index 418e99c8e18e..1ace341a0ff4 100644 > --- a/hw/display/macfb.c > +++ b/hw/display/macfb.c > @@ -714,6 +714,7 @@ static void macfb_nubus_set_irq(void *opaque, int n, int level) > > static void macfb_nubus_realize(DeviceState *dev, Error **errp) > { > + ERRP_GUARD(); > NubusDevice *nd = NUBUS_DEVICE(dev); > MacfbNubusState *s = NUBUS_MACFB(dev); > MacfbNubusDeviceClass *ndc = NUBUS_MACFB_GET_CLASS(dev); The dereference is ndc->parent_realize(dev, errp); if (*errp) { return; } We check *errp, because neither the callback returns void. Reviewed-by: Markus Armbruster