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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 5F1F8C433C1 for ; Fri, 19 Mar 2021 16:00:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 31F5F61975 for ; Fri, 19 Mar 2021 16:00:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230215AbhCSQAL (ORCPT ); Fri, 19 Mar 2021 12:00:11 -0400 Received: from mga02.intel.com ([134.134.136.20]:32284 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230063AbhCSP7s (ORCPT ); Fri, 19 Mar 2021 11:59:48 -0400 IronPort-SDR: p+aKNGHQWuFgnUqK/ESyaLj11nLS/9V8vjZu2hzcg+RARfleWuM5mX07vnmO4OGKXRM/4HsVZX 7QqhpRPGWd7g== X-IronPort-AV: E=McAfee;i="6000,8403,9928"; a="177048951" X-IronPort-AV: E=Sophos;i="5.81,262,1610438400"; d="scan'208";a="177048951" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Mar 2021 08:59:47 -0700 IronPort-SDR: chN/95p+sd/RiH9NMoqV28SSONxyOqcql63k4mLGL+z/pUp98J4rh+ezsQa3Tf5rv/ym0xjeEI Q29wyFt2qaOQ== X-IronPort-AV: E=Sophos;i="5.81,262,1610438400"; d="scan'208";a="406840294" Received: from hyunyi-mobl1.amr.corp.intel.com (HELO [10.212.50.74]) ([10.212.50.74]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Mar 2021 08:59:46 -0700 Subject: Re: [PATCH] x86/sgx: Avoid returning NULL in __sgx_alloc_epc_page() To: Borislav Petkov , Jarkko Sakkinen Cc: Kai Huang , x86@kernel.org, linux-sgx@vger.kernel.org, dave.hansen@linux.intel.com, linux-kernel@vger.kernel.org References: <20210319040602.178558-1-kai.huang@intel.com> <20210319084523.GA6251@zn.tnic> <20210319220141.8bf20c54fdb06c6f93cde448@intel.com> <20210319145931.GH6251@zn.tnic> <20210319155249.GK6251@zn.tnic> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210319155249.GK6251@zn.tnic> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/19/21 8:52 AM, Borislav Petkov wrote: > On Fri, Mar 19, 2021 at 05:22:56PM +0200, Jarkko Sakkinen wrote: >> I did misread it for the first time. >> >> So let's sanity: you *are* going to squash the patches together because >> that way it's factors easier to backport the whole thing? >> >> Is this the correct understanding? > I squashed Kai's fix because I don't want to break people's bisection if > they land between your patch and his fix. They're already troubled enough > chasing an issue, don't want to have them get a NULL ptr in sgx land. > > Now, looking at dhansen's fix: what can happen if nid is uninitialized? > AFAICT, we'll end up in > > static inline int __next_node(int n, const nodemask_t *srcp) > { > return min_t(int,MAX_NUMNODES,find_next_bit(srcp->bits, MAX_NUMNODES, n+1)); > } > > with n uninitialized and depending on its value it'll either return > MAX_NUMNODES so we'll try to allocate on the first node or try to > allocate on some other node. > > Now, if you think that that is still problematic enough for enclave > creation, then I'll fold his patch too. > > So yes, the main reason is usability and not breaking bisection. > > So, what would you prefer? It's probably best to squash my patch in. The uninitialized value could *theoretically* cause the search to start at the wrong node and then end before every node has been visited. That could cause premature allocation failures. But, I seriously doubt anyone will notice either way.