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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 6B791C4361B for ; Wed, 16 Dec 2020 11:23:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B9B232255F for ; Wed, 16 Dec 2020 11:23:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B9B232255F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CB13C6B0070; Wed, 16 Dec 2020 06:23:00 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C3B876B0071; Wed, 16 Dec 2020 06:23:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B02706B0073; Wed, 16 Dec 2020 06:23:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0167.hostedemail.com [216.40.44.167]) by kanga.kvack.org (Postfix) with ESMTP id 9BA786B0070 for ; Wed, 16 Dec 2020 06:23:00 -0500 (EST) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 5FE99181AEF21 for ; Wed, 16 Dec 2020 11:23:00 +0000 (UTC) X-FDA: 77598908520.26.back08_35186902742b Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id 421311804B656 for ; Wed, 16 Dec 2020 11:23:00 +0000 (UTC) X-HE-Tag: back08_35186902742b X-Filterd-Recvd-Size: 3678 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by imf49.hostedemail.com (Postfix) with ESMTP for ; Wed, 16 Dec 2020 11:22:59 +0000 (UTC) IronPort-SDR: kWSoRs65YiIsstYCmoKJV1d8cXjoXoIT0U7Ll+H6U15X7RMkCCMfe54qYKcH+6ZWr+rrhleKa6 MfMkdhcWpjIg== X-IronPort-AV: E=McAfee;i="6000,8403,9836"; a="236628754" X-IronPort-AV: E=Sophos;i="5.78,424,1599548400"; d="scan'208";a="236628754" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Dec 2020 03:22:57 -0800 IronPort-SDR: SwBmQ5tLg7ZBVQM4wUZizehwFJf/df9eiAFYeevLRGvLTyFB+ooI7e3QelpBTlda8lxMtKIS1x 0FSH5bXgADpA== X-IronPort-AV: E=Sophos;i="5.78,424,1599548400"; d="scan'208";a="384425397" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Dec 2020 03:22:50 -0800 Received: from andy by smile with local (Exim 4.94) (envelope-from ) id 1kpUuN-00Ek3v-5T; Wed, 16 Dec 2020 13:23:51 +0200 Date: Wed, 16 Dec 2020 13:23:51 +0200 From: Andy Shevchenko To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: Andrew Morton , airlied@linux.ie, alexander.shishkin@linux.intel.com, bgolaszewski@baylibre.com, bp@alien8.de, bp@suse.de, cl@linux.com, daniel.vetter@ffwll.ch, daniel@ffwll.ch, gustavo@padovan.org, iamjoonsoo.kim@lge.com, james.morse@arm.com, jasowang@redhat.com, linus.walleij@linaro.org, linux-mm@kvack.org, maarten.lankhorst@linux.intel.com, mchehab@kernel.org, mm-commits@vger.kernel.org, mripard@kernel.org, mst@redhat.com, penberg@kernel.org, perex@perex.cz, rientjes@google.com, rric@kernel.org, sumit.semwal@linaro.org, tiwai@suse.com, tiwai@suse.de, tony.luck@intel.com, torvalds@linux-foundation.org, tzimmermann@suse.de, vbabka@suse.cz Subject: Re: [patch 012/200] mm: slab: clarify krealloc()'s behavior with __GFP_ZERO Message-ID: <20201216112351.GZ4077@smile.fi.intel.com> References: <20201215030350.xC0HoDUgG%akpm@linux-foundation.org> <2172e342-e73f-a759-fce5-8b94daafd506@amd.com> <20201215190840.GU4077@smile.fi.intel.com> <14a1a889-fc99-47df-c336-1727e8e22b42@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <14a1a889-fc99-47df-c336-1727e8e22b42@amd.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Dec 16, 2020 at 08:47:25AM +0100, Christian K=F6nig wrote: > Am 15.12.20 um 20:08 schrieb Andy Shevchenko: > > On Tue, Dec 15, 2020 at 03:30:44PM +0100, Christian K=F6nig wrote: > > > Am 15.12.20 um 04:03 schrieb Andrew Morton: > > ... > >=20 > > > Question: Can the fact that __GFP_ZERO is effectively ignored cause= an > > > information leak if new size is larger than old size and the array = is > > > somehow copied to user space? > > >=20 > > > I think the answer is no, but just wanted to double check. Maybe we= should > > > note that here. > > kmalloc()/kmalloc_array()/etc has the same. Should it be mentioned th= ere as well? >=20 > No, they don't. If kmalloc()/kmalloc_array() would ignore __GFP_ZERO we > would have quite a problem. >=20 > It is only krealloc()/krealloc_array() which ignore __GFP_ZERO when the= y > don't reallocate memory because newsize is smaller than oldsize. In oth= er > words the freed up space is not cleared in any way. Yes, true. So, you meant that comment now a bit misleading. I agree. --=20 With Best Regards, Andy Shevchenko