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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=unavailable 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 41175C282CC for ; Tue, 5 Feb 2019 12:35:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F400B20844 for ; Tue, 5 Feb 2019 12:35:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="DRBpNRi/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F400B20844 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=alien8.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 96A768E0087; Tue, 5 Feb 2019 07:35:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 919008E0083; Tue, 5 Feb 2019 07:35:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8303B8E0087; Tue, 5 Feb 2019 07:35:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by kanga.kvack.org (Postfix) with ESMTP id 2CDB08E0083 for ; Tue, 5 Feb 2019 07:35:41 -0500 (EST) Received: by mail-wr1-f70.google.com with SMTP id z18so1079466wrh.19 for ; Tue, 05 Feb 2019 04:35:41 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:date:from:to:cc:subject :message-id:references:mime-version:content-disposition:in-reply-to :user-agent; bh=qy0tAhFBRu2LNdPFTbVIGZuXfaj4t8RKzaRmpgJF9M0=; b=VhZ+0NaXBMi6NIeTBwGu3pbpFMwREVoaStlAVw/0sD5Ye4YCGFX6QH6GyvMWBM3iz4 dOTGzv8XtjnUw5SDba3P4T3VCiZ7c15EoTphsPck8VRSHnLKVssfsX3HI6Y3si+0ylfE B/GZR2eBYa18g3zklqZfd0cq0/oSMDlJAwH5ygby3UUrbzLd6yvDz+qwiZ2EvqzGbMiW slOFQC1hnIqwXSh7MCUbivxmMWhmkxPlF7Ogis1Acmex723eRFHOUewAdzNoPYoHG7UR ifst3vuIzU2iZfRtyXBQQy5PryQIGb7lqjVGezgjTqPh9PFF7DmRmR8oNPNg3PU1Brwp 2wQQ== X-Gm-Message-State: AHQUAuZY9m5nOkQZKv3AXtDcE7NLjX3hvXVIrpZdedwrK99BC0p0JYtJ BpHZtJH9WXlDmB2kzbifcj8A9RVOx7mVN2OeS97TB0l6d+aogkcDw/5E9ASAR+hf9XNK5nk5Xsu SbOSR/2fxvtEBc37WnPVKfzfqExKU3xY/2rAhkfUOQzCY0SdZw7dNsKFCsMuD/9Dstg== X-Received: by 2002:a1c:35ca:: with SMTP id c193mr3531015wma.146.1549370140735; Tue, 05 Feb 2019 04:35:40 -0800 (PST) X-Google-Smtp-Source: AHgI3IYj2CiBUasBZlgj2Tq1DQdieD1PTQtLlPKqlUXfJY2Pk4iyBdQIveb7IGoA5sgpfegNkHCU X-Received: by 2002:a1c:35ca:: with SMTP id c193mr3530965wma.146.1549370139874; Tue, 05 Feb 2019 04:35:39 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1549370139; cv=none; d=google.com; s=arc-20160816; b=CeYsjLy6dyyG+1x2hPqAJZTawVB1fmBIWYWgJQ8hTHTfevlHIoC1FfkFOBualDEudx OIoj7r8q3kqFh+ksb0HKUwKn404D4QyHFV/9F1v2h2p8KSHFjab9tAyjRxGSj1gc2BRN idklg5E/eC4UBjFStpjaU4QM9YLWZ/RhERjCY7VpE3vuaLtuHLJ9d+le73VcZmU7hSrP o9VgCK9J/YAeGGpZLu1C79zSDSk42F0tnL5YDcltMGgz16fOB7vss0XfMdjApqSRSSe4 jDQ9+YID6AocP/Ul1aGtf8If0g8X8CVXxCQt0Su1IyYVkZ6w+N4KRcwsa53VZbvhP2+9 vOGA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature; bh=qy0tAhFBRu2LNdPFTbVIGZuXfaj4t8RKzaRmpgJF9M0=; b=HUW+mqlfpz665nRushs2Cruk/ZdU6fyMG+ww8wl0NCDXhdWTP8tOGpkhPTyq91zsnx L1p3fvnN0MUiTwMIiuOS5q/00aeDLL6hGoHj0CT7Ydz/Kt7A88DXqYSlMZ2bBEG5IUBz 6xdAaIvTi9Ld2ZaDj4d3CtmJ43/c/nk13pT6dbc8STsDhSS5e0DsIA+0ukzDCSPzwEwE v6uoaXMnzVY9GIfdzaKBfX7fV0Y6d+3aKjsQ3w35n1pDR0SD2zUfw3cYyU2nYZvxB3rQ I371mreOknu6W1Z8mUrVbEIOFi12X7SrG2+5xpSlppL0ygw5CJXDp46wqz0dfjk03HLZ svxw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@alien8.de header.s=dkim header.b="DRBpNRi/"; spf=pass (google.com: domain of bp@alien8.de designates 5.9.137.197 as permitted sender) smtp.mailfrom=bp@alien8.de; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=alien8.de Received: from mail.skyhub.de (mail.skyhub.de. [5.9.137.197]) by mx.google.com with ESMTPS id l14si13623068wrm.131.2019.02.05.04.35.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 Feb 2019 04:35:39 -0800 (PST) Received-SPF: pass (google.com: domain of bp@alien8.de designates 5.9.137.197 as permitted sender) client-ip=5.9.137.197; Authentication-Results: mx.google.com; dkim=pass header.i=@alien8.de header.s=dkim header.b="DRBpNRi/"; spf=pass (google.com: domain of bp@alien8.de designates 5.9.137.197 as permitted sender) smtp.mailfrom=bp@alien8.de; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=alien8.de Received: from zn.tnic (p200300EC2BCB6B00551F5C4602011D50.dip0.t-ipconnect.de [IPv6:2003:ec:2bcb:6b00:551f:5c46:201:1d50]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id F06221EC02AE; Tue, 5 Feb 2019 13:35:38 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1549370139; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=qy0tAhFBRu2LNdPFTbVIGZuXfaj4t8RKzaRmpgJF9M0=; b=DRBpNRi/AE/ddp/N7PrPG+UELrdIUTt+dE0vNyWk0LmyVCMEV87pZqiHROizDHuJ+chxOY wbn2bNksDewsX0nnPJonclKBTBPDLlbqaAPJQfBgIqfugNE/JGPoeg3HX/yPwElmarfcka AkZNyj+mTvYwgUo4/GGLwq7WnhR/PHo= Date: Tue, 5 Feb 2019 13:35:33 +0100 From: Borislav Petkov To: Peter Zijlstra Cc: Rick Edgecombe , Andy Lutomirski , Ingo Molnar , linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com, Thomas Gleixner , Nadav Amit , Dave Hansen , linux_dti@icloud.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, akpm@linux-foundation.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, will.deacon@arm.com, ard.biesheuvel@linaro.org, kristen@linux.intel.com, deneen.t.dock@intel.com, Nadav Amit , Kees Cook , Dave Hansen , Masami Hiramatsu Subject: Re: [PATCH v2 06/20] x86/alternative: use temporary mm for text poking Message-ID: <20190205123533.GN21801@zn.tnic> References: <20190129003422.9328-1-rick.p.edgecombe@intel.com> <20190129003422.9328-7-rick.p.edgecombe@intel.com> <20190205095853.GJ21801@zn.tnic> <20190205113146.GP17528@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190205113146.GP17528@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.004625, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Feb 05, 2019 at 12:31:46PM +0100, Peter Zijlstra wrote: > ... > > So while in general I agree with BUG_ON() being undesirable, I think > liberal sprinking in text_poke() is fine; you really _REALLY_ want this > to work or fail loudly. Text corruption is just painful. Ok. It would be good to have the gist of this sentiment in a comment above it so that it is absolutely clear why we're doing it. And since text_poke() can't fail, then it doesn't need a retval too. AFAICT, nothing is actually using it. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.