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 21C61C282D7 for ; Tue, 5 Feb 2019 12:35:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC6712083B 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/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726550AbfBEMfl (ORCPT ); Tue, 5 Feb 2019 07:35:41 -0500 Received: from mail.skyhub.de ([5.9.137.197]:51226 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725947AbfBEMfl (ORCPT ); Tue, 5 Feb 2019 07:35:41 -0500 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) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk 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.