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=-6.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,T_DKIMWL_WL_HIGH autolearn=ham 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 D94DFC4321A for ; Mon, 10 Jun 2019 20:44:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0D4E206E0 for ; Mon, 10 Jun 2019 20:44:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="e2CZUihY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389823AbfFJUo5 (ORCPT ); Mon, 10 Jun 2019 16:44:57 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:45655 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389331AbfFJUo5 (ORCPT ); Mon, 10 Jun 2019 16:44:57 -0400 Received: by mail-pf1-f193.google.com with SMTP id s11so5946390pfm.12 for ; Mon, 10 Jun 2019 13:44:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=gFNF363RDc/XdYA/qTwjgCIxHifrzxkDYNHAq+P6+0s=; b=e2CZUihYvTafnYYHa056o7+bSSzfL1Ff4bnwCZJQJRYmAZXuNLs4PAqpQu2Hc877TH oVAuevfcQD/nV5NtqR0pXt0JiPAQE1f+NvWQAA/cDZJNvE1WXgUMc4qET2B9/WPz4AZI JaHy3eRaR0YvxNOAZ1ua6HxHSX0pLNCycB4r0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=gFNF363RDc/XdYA/qTwjgCIxHifrzxkDYNHAq+P6+0s=; b=hJLuz0s/mGEgPboKnmltt4+P8EfUXzj11FQXAJBGSyffSF/K1wzv46fQZYxSWEdVZR 1BGYeUQYtj5m90awlTIk9C/FcNm2fdvovdCyndFbtX+ijzOrt9c8xLdLOlsfUm83v+DY ptyGBDTF1sr2UjCtMusbtzn9I3U4V5wkqvObS/umCe1VqHWvy2SqoSxbuAcLERtZvt6K vSiulW4mPfK131jwIcIEuVnI2YX2qwkyytuWPSR/Nf53Sta24+USmYhOBaekvJUel+aY NyowNK1D/IWNKlne+uy0Ddce9ddEmDdj0rhyHavrBgLCMD7aHOP9FE4TF0FKJ3lCAk1K L3Kw== X-Gm-Message-State: APjAAAV66PY4rKtkVT7a4R7+gXjtmvitEHK35bK1LvPyr60uotaQM4Cg Dmi/Cx/97eaaCKAce57fX/7T+w== X-Google-Smtp-Source: APXvYqybNR2PIaiWpTHApIK7YBw6IPSSen1QXNs1Vc9JJjXcnCU9uxUQ/3zVX0wDRddk2VworcnaBw== X-Received: by 2002:a17:90a:b00b:: with SMTP id x11mr23332542pjq.120.1560199496619; Mon, 10 Jun 2019 13:44:56 -0700 (PDT) Received: from www.outflux.net (173-164-112-133-Oregon.hfc.comcastbusiness.net. [173.164.112.133]) by smtp.gmail.com with ESMTPSA id a192sm876392pfa.84.2019.06.10.13.44.55 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 10 Jun 2019 13:44:55 -0700 (PDT) Date: Mon, 10 Jun 2019 13:44:55 -0700 From: Kees Cook To: Andy Lutomirski Cc: x86@kernel.org, LKML , Borislav Petkov , Kernel Hardening , Peter Zijlstra , Thomas Gleixner Subject: Re: [PATCH 5/5] x86/vsyscall: Change the default vsyscall mode to xonly Message-ID: <201906101344.018BE4C5C1@keescook> References: <25fd7036cefca16c68ecd990e05e05a8ad8fe8b2.1560198181.git.luto@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <25fd7036cefca16c68ecd990e05e05a8ad8fe8b2.1560198181.git.luto@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 10, 2019 at 01:25:31PM -0700, Andy Lutomirski wrote: > The use case for full emulation over xonly is very esoteric. Let's > change the default to the safer xonly mode. Perhaps describe the esoteric cases here (and maybe in the Kconfig help text)? That should a user determine if they actually need it. (What would the failure under xonly look like for someone needing emulate?) -Kees > > Cc: Kees Cook > Cc: Borislav Petkov > Cc: Kernel Hardening > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Signed-off-by: Andy Lutomirski > --- > arch/x86/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 054033cc4b1b..e56f33e6b045 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -2280,7 +2280,7 @@ config COMPAT_VDSO > choice > prompt "vsyscall table for legacy applications" > depends on X86_64 > - default LEGACY_VSYSCALL_EMULATE > + default LEGACY_VSYSCALL_XONLY > help > Legacy user code that does not know how to find the vDSO expects > to be able to issue three syscalls by calling fixed addresses in > -- > 2.21.0 > -- Kees Cook