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[195.135.220.15]) by mx.google.com with ESMTPS id t1si28611ejz.165.2019.05.29.09.25.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 May 2019 09:25:34 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 206D5ADEA; Wed, 29 May 2019 16:25:34 +0000 (UTC) Date: Wed, 29 May 2019 18:25:32 +0200 From: Michal Hocko To: Dianzhang Chen Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/slab_common.c: fix possible spectre-v1 in kmalloc_slab() Message-ID: <20190529162532.GG18589@dhcp22.suse.cz> References: <1559133448-31779-1-git-send-email-dianzhangchen0@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1559133448-31779-1-git-send-email-dianzhangchen0@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 29-05-19 20:37:28, Dianzhang Chen wrote: [...] > @@ -1056,6 +1057,7 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags) > if (!size) > return ZERO_SIZE_PTR; > > + size = array_index_nospec(size, 193); > index = size_index[size_index_elem(size)]; What is this 193 magic number? -- Michal Hocko SUSE Labs