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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 82C55C48BE5 for ; Wed, 16 Jun 2021 20:01:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6034361351 for ; Wed, 16 Jun 2021 20:01:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233036AbhFPUDV (ORCPT ); Wed, 16 Jun 2021 16:03:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43534 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232953AbhFPUDT (ORCPT ); Wed, 16 Jun 2021 16:03:19 -0400 Received: from mail-lj1-x22c.google.com (mail-lj1-x22c.google.com [IPv6:2a00:1450:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0665FC061574 for ; Wed, 16 Jun 2021 13:01:13 -0700 (PDT) Received: by mail-lj1-x22c.google.com with SMTP id l15so1263051lje.10 for ; Wed, 16 Jun 2021 13:01:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=y0sGanNeM+6nVMH7hMipVVh7kfFvtaj9v71nplXpGOQ=; b=W2AITzayliTdBtw+P2eGCat6m1fvimytrfbjpYp3F+ZqA7U78mdL6p9s1QlqYnA0Cu HmuuCHptbwVi95FtTdSDCMlLPBnLl9I3IjPOnYExv6QFeCUpcrP5yEPGt2AUEAL6rQRa AVA3P5mSOxUsuokFD59yB5+vElkaqAzJ+n8vs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=y0sGanNeM+6nVMH7hMipVVh7kfFvtaj9v71nplXpGOQ=; b=a1atSRuC0GxBz+tqtCX5jQqOASOizakYBJLPSQQDTzoDeITdSt1Vr2ndSeCisRj7nh OuFUo5N/Yf9LLhyeKiw48JFATN7xXV4mzRjBXtV55KS1gFBoO09tUkLKoqhvJoKC9uTe +kLTGYaY0+nyWj8TBgGacrplMSFK4yaE0tJfqnAvR+qyTdtSN77Qo0nZAAt2yGWdvkR+ xITT7sHGGk+vxSrHQy4hCoKQ1IXxkaF4tNyygGFD0cnlBH9DNHYTEMgdcMQRM63QLXC/ lprgS4TEwNsROLRP1IkhE6xuKxC9Wq4I86f4TP4BLWm+w5uxrTaKYgV61QZtPi8n+JIi rdmg== X-Gm-Message-State: AOAM531ajQRi93e6aJVWUdoD4MtP+slBNf8p6eqT33Kg5qux2YnH86Wx G2grHXkAUm9mpN1KzqyVwk3alQC3S46hzkaQ7+w= X-Google-Smtp-Source: ABdhPJwv63BO8jNlmcqtk7tVY5O80LkWh3HBX1FMP/x8kB9x1nv+cwT2y2FT5YrtRip4Qg+91LD8KA== X-Received: by 2002:a2e:9605:: with SMTP id v5mr1321739ljh.223.1623873671078; Wed, 16 Jun 2021 13:01:11 -0700 (PDT) Received: from mail-lf1-f45.google.com (mail-lf1-f45.google.com. [209.85.167.45]) by smtp.gmail.com with ESMTPSA id z10sm344035lfj.221.2021.06.16.13.01.09 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Jun 2021 13:01:09 -0700 (PDT) Received: by mail-lf1-f45.google.com with SMTP id r198so6224408lff.11 for ; Wed, 16 Jun 2021 13:01:09 -0700 (PDT) X-Received: by 2002:a05:6512:3d13:: with SMTP id d19mr1037501lfv.41.1623873668703; Wed, 16 Jun 2021 13:01:08 -0700 (PDT) MIME-Version: 1.0 References: <87sg1p30a1.fsf@disp2133> <87pmwsytb3.fsf@disp2133> <87sg1lwhvm.fsf@disp2133> <6e47eff8-d0a4-8390-1222-e975bfbf3a65@gmail.com> <924ec53c-2fd9-2e1c-bbb1-3fda49809be4@gmail.com> <87eed4v2dc.fsf@disp2133> <5929e116-fa61-b211-342a-c706dcb834ca@gmail.com> <87fsxjorgs.fsf@disp2133> <87zgvqor7d.fsf_-_@disp2133> <87mtrpg47k.fsf@disp2133> <87pmwlek8d.fsf_-_@disp2133> <87k0mtek4n.fsf_-_@disp2133> In-Reply-To: <87k0mtek4n.fsf_-_@disp2133> From: Linus Torvalds Date: Wed, 16 Jun 2021 13:00:52 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack To: "Eric W. Biederman" Cc: Michael Schmitz , linux-arch , Jens Axboe , Oleg Nesterov , Al Viro , Linux Kernel Mailing List , Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , Geert Uytterhoeven , linux-m68k , Arnd Bergmann , Ley Foon Tan , Tejun Heo , Kees Cook Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 16, 2021 at 11:32 AM Eric W. Biederman wrote: > > Prevent security holes by recording when all of the registers are > available so generic code changes do not result in security holes > on alpha. Please no, not this way. ldl/stc is extremely expensive on some alpha cpus. I really think thatTIF_ALLREGS_SAVED bit isn't worth it, except perhaps for debugging. And even for debugging, I think it would be both easier and cheaper to just add a magic word to the entry stack instead. Linus