From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4/Dma8w7R1ZqhJaSmHip0I13Hn7vytfVQ8L0MBmogCevr5HELxQqGdMCyxL/c0bO58vdav5 ARC-Seal: i=1; a=rsa-sha256; t=1524081030; cv=none; d=google.com; s=arc-20160816; b=jKjtsgfATLU9rCyVL+Q9ZdklTkHnOIWdq6bDiE9pDmwYHusbQnUQRbMN7UGDet4c9i gA77KvGQKlzu1cyZZemd7pXcXoq86XR5plKvNUFG+INkuK+DDgW/zz4UeNzmcEn1ilAI 2shJP5qEehnym2g52/3bfzocA0Y9oAUT0Ix1bkPrrkaSUAHK7ljAkJOFAWun/USBASd5 lt/73UC+t3ZgSuhXqQBftfxUXP9EKcDBYfhT6hu3+xHYgvMdbLfNbKRvk8arj047RUrp paX0Miu3YuCDP4G9gXOmFxUEOeTJfGVuny0Riyl9Vj97ujLe3hrbFeR2mdDv1+dmpTtl dj8Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:delivered-to:list-id :list-subscribe:list-unsubscribe:list-help:list-post:precedence :mailing-list:arc-authentication-results; bh=TT0oAoffY/QgdwF87ie0MQODftxNQDFM281k2xRoB84=; b=osDPXSol3w4UZsTYUw6Fcb3CoilNmSN/jG12EI/02iHTtf5wsfloH/In6FduWA9LxF SKcaATZPYWmjNagDkGPBUjWSbT5cZlx+U/yyg3vl/fDbeYxe6DMAKyqL6d/cc4q3gkYT we+nFa7x83hweJnb3/N4D2cJarkcksKQAx8n+vNYVZCwVr4U1l27UBI99OtQMHXix0Z1 rBeP2QX+OY8iehGmKhGHoWybkFBsCtw0/L6cwEA4wXC13Uy9LGaRBn0T8b9oUE2jpak8 jP52WSQQa/plMHpkZCImlW8cEPhNc4bZK9qoRG0N26IhhOspYeYVfVG0C6EWhFMHv7KG SBpg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of kernel-hardening-return-13046-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-13046-gregkh=linuxfoundation.org@lists.openwall.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of kernel-hardening-return-13046-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-13046-gregkh=linuxfoundation.org@lists.openwall.com Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm List-Post: List-Help: List-Unsubscribe: List-Subscribe: Date: Wed, 18 Apr 2018 12:50:08 -0700 From: Andrew Morton To: Kees Cook Cc: Michal Hocko , Andy Lutomirski , Laura Abbott , Rasmus Villemoes , LKML , Kernel Hardening Subject: Re: [PATCH v2] fork: Unconditionally clear stack on fork Message-Id: <20180418125008.203632feeaf0cac4e51c5b79@linux-foundation.org> In-Reply-To: References: <20180221021659.GA37073@beast> <20180221102933.GD2231@dhcp22.suse.cz> <20180221125914.dc95830eada5fb958c13e36b@linux-foundation.org> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1592975104699087561?= X-GMAIL-MSGID: =?utf-8?q?1598114790019841577?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, 18 Apr 2018 09:38:07 -0700 Kees Cook wrote: > >> So some quite careful quantitative testing is needed here, methinks. > > > > Well, I did some more with perf and cycle counts on running 100,000 > > execs of /bin/true. > > > > before: > > Cycles: 218858861551 218853036130 214727610969 227656844122 224980542841 > > Mean: 221015379122.60 > > Std Dev: 4662486552.47 > > > > after: > > Cycles: 213868945060 213119275204 211820169456 224426673259 225489986348 > > Mean: 217745009865.40 > > Std Dev: 5935559279.99 > > > > It continues to look like it's faster, though the deviation is rather > > wide, but I'm not sure what I could do that would be less noisy. I'm > > open to ideas! > > Friendly ping. Andrew, can you add this to -mm? I did so on Feb 21 but didn't merge it up because I'd told myself that careful perf testing is needed. I guess we've sufficiently ticked that box. Kind of. Maybe. Oh well, it's easy enough to revert. I'll add it to the next batch-for-Linus.