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[192.55.52.88]) by mx.google.com with ESMTPS id f127si2719899pfc.176.2019.04.18.09.35.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Apr 2019 09:35:44 -0700 (PDT) Received-SPF: pass (google.com: domain of dave.hansen@intel.com designates 192.55.52.88 as permitted sender) client-ip=192.55.52.88; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 18 Apr 2019 09:35:33 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,366,1549958400"; d="scan'208";a="224675019" Received: from ray.jf.intel.com (HELO [10.7.201.126]) ([10.7.201.126]) by orsmga001.jf.intel.com with ESMTP; 18 Apr 2019 09:35:33 -0700 Subject: Re: [PATCH 1/3] mm: security: introduce the init_allocations=1 boot option To: Alexander Potapenko , akpm@linux-foundation.org, cl@linux.com, dvyukov@google.com, keescook@chromium.org, labbott@redhat.com Cc: linux-mm@kvack.org, linux-security-module@vger.kernel.org, kernel-hardening@lists.openwall.com References: <20190418154208.131118-1-glider@google.com> <20190418154208.131118-2-glider@google.com> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190418154208.131118-2-glider@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit 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 4/18/19 8:42 AM, Alexander Potapenko wrote: > This option adds the possibility to initialize newly allocated pages and > heap objects with zeroes. This is needed to prevent possible information > leaks and make the control-flow bugs that depend on uninitialized values > more deterministic. Isn't it better to do this at free time rather than allocation time? If doing it at free, you can't even have information leaks for pages that are in the allocator.