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 X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 01C69C04EB8 for ; Mon, 10 Dec 2018 20:42:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AF39220821 for ; Mon, 10 Dec 2018 20:42:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AF39220821 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729314AbeLJUmQ (ORCPT ); Mon, 10 Dec 2018 15:42:16 -0500 Received: from mga11.intel.com ([192.55.52.93]:46031 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727598AbeLJUmP (ORCPT ); Mon, 10 Dec 2018 15:42:15 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Dec 2018 12:42:15 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,339,1539673200"; d="scan'208";a="117229612" Received: from rchatre-mobl.amr.corp.intel.com (HELO [10.24.14.96]) ([10.24.14.96]) by orsmga002.jf.intel.com with ESMTP; 10 Dec 2018 12:42:14 -0800 Subject: Re: [PATCH] x86/resctrl: Fix rdt_find_domain() return value checks To: Borislav Petkov Cc: tglx@linutronix.de, fenghua.yu@intel.com, tony.luck@intel.com, jithu.joseph@intel.com, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org References: <20181210191311.GC5482@zn.tnic> From: Reinette Chatre Message-ID: <40422756-cef4-38b1-8554-c99e7bcb7765@intel.com> Date: Mon, 10 Dec 2018 12:42:14 -0800 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181210191311.GC5482@zn.tnic> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Boris, On 12/10/2018 11:13 AM, Borislav Petkov wrote: > On Wed, Nov 28, 2018 at 10:20:27AM -0800, Reinette Chatre wrote: >> rdt_find_domain() may return an ERR_PTR(), NULL, or a pointer to struct >> rdt_domain. It is thus required that the return value be checked for the >> possibility of an ERR_PTR as well as NULL. > > Well, it returns ERR_PTR(id) but code which uses ERR_PTR passes in an -E > value, for example ERR_PTR(-EINVAL) or so, and not an id. > > And that might work now if id fits within that MAX_ERRNO range - I'm > looking at include/linux/err.h - but that's still fragile. > Thank you for catching this. It does seem as though things work at this time since rdt_find_domain() contains: if (id < 0) return ERR_PTR(id); and from what I can tell the only possible negative value of id is -1. As you note, this is fragile. Additionally the error, if intending to use -E values, does not reflect the error (since -1 would mean EPERM). Would you be ok if the above is changed to if (id < 0) return ERR_PTR(-ENOENT); as part of this patch? Looking at rdtgroup_mondata_show() is does seem as though ENOENT is the actual intended error value, although ENODEV could perhaps also be considered since such a result reflects that a particular cache instance could not be found. Thank you! Reinette