From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.90_1) id 1rfEOU-0003ds-J4 for mharc-qemu-trivial@gnu.org; Wed, 28 Feb 2024 02:30:22 -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 1rfEOS-0003dC-Pg for qemu-trivial@nongnu.org; Wed, 28 Feb 2024 02:30:20 -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 1rfEOQ-00009E-1h for qemu-trivial@nongnu.org; Wed, 28 Feb 2024 02:30:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709105416; 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=Fsb6wqWPtLgyEJyteYP5HWHeRZOILnjmTS6NLknJUXY=; b=U3+I8PVByQWSxGbTvQRwUIIXoB9YW/vuKxaKs8fHF4Fytx59IFdLYNzZLzMZTvAlhy64et AqtJBu3zURV7LsSA67+JxeMO6fkPMkpJm4vE5NIoZzbdj4wIoxB1XdITRElL0iJ6hqRVAp Po0/WtjKz2V5G8jtZZ5mr/4TFQ3tXfA= 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-59-ziVIXGdjNku_CInty1az6Q-1; Wed, 28 Feb 2024 02:30:14 -0500 X-MC-Unique: ziVIXGdjNku_CInty1az6Q-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (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 4B34D3806703; Wed, 28 Feb 2024 07:30:13 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.4]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5CAD9492BC6; Wed, 28 Feb 2024 07:30:12 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 3979921E66F9; Wed, 28 Feb 2024 08:30:11 +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?= , Paolo Bonzini , Michael Tokarev , qemu-devel@nongnu.org, qemu-arm@nongnu.org, qemu-trivial@nongnu.org, Zhao Liu Subject: Re: [PATCH v2 1/7] hw/cxl/cxl-host: Fix missing ERRP_GUARD() in cxl_fixed_memory_window_config() In-Reply-To: <20240223085653.1255438-2-zhao1.liu@linux.intel.com> (Zhao Liu's message of "Fri, 23 Feb 2024 16:56:47 +0800") References: <20240223085653.1255438-1-zhao1.liu@linux.intel.com> <20240223085653.1255438-2-zhao1.liu@linux.intel.com> Date: Wed, 28 Feb 2024 08:30:11 +0100 Message-ID: <877cip3v24.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 10.11.54.9 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=-0.088, 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=ham 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, 28 Feb 2024 07:30:21 -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. > ... > * 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. > > But in cxl_fixed_memory_window_config(), @errp is dereferenced in 2 > places without ERRP_GUARD(): > > fw->enc_int_ways = cxl_interleave_ways_enc(fw->num_targets, errp); > if (*errp) { > return; > } > > and > > fw->enc_int_gran = > cxl_interleave_granularity_enc(object->interleave_granularity, > errp); > if (*errp) { > return; > } No need to quote the dereferences in full. But in cxl_fixed_memory_window_config(), @errp is dereferenced in 2 places without ERRP_GUARD(). In these two places, we check "*errp", because neither function would do. Same for the other commit messages. Hardly worth a respin, though :) > For the above 2 places, we check "*errp", because neither function > returns a suitable error code. And since machine_set_cfmw() - the caller > of cxl_fixed_memory_window_config() - doesn't get the NULL @errp > parameter as the "set" method of object property, > cxl_fixed_memory_window_config() hasn't triggered the bug that > dereferencing the NULL @errp. > > To follow the requirement of @errp, add missing ERRP_GUARD() in > cxl_fixed_memory_window_config(). > > Suggested-by: Markus Armbruster > Signed-off-by: Zhao Liu > Reviewed-by: Markus Armbruster > --- > Suggested by credit: > Markus: Referred his explanation about ERRP_GUARD(). > --- > v2: > * Add the @errp dereference code in commit message to make review > easier. (Markus) > --- > hw/cxl/cxl-host.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/hw/cxl/cxl-host.c b/hw/cxl/cxl-host.c > index 2aa776c79c74..c5f5fcfd64d0 100644 > --- a/hw/cxl/cxl-host.c > +++ b/hw/cxl/cxl-host.c > @@ -26,6 +26,7 @@ static void cxl_fixed_memory_window_config(CXLState *cxl_state, > CXLFixedMemoryWindowOptions *object, > Error **errp) > { > + ERRP_GUARD(); > g_autofree CXLFixedWindow *fw = g_malloc0(sizeof(*fw)); > strList *target; > int i;