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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D0932C43331 for ; Wed, 1 Apr 2020 23:56:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A1333206D3 for ; Wed, 1 Apr 2020 23:56:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585785363; bh=8MW4IauE+eEnJhMmqznDU0abqEG4r/721eygO1jhEpc=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=blQF7Pxurtt5ThlCNNVTQK5aGUipKFrhHm7q0dfaeZfFIzltABZg60l/sNFVO8oyP /fN9ivWO5eYAUaHBQOQ6wkUDryA+AvFXzpvDtX7YWAuXtmzETKGoVMwjfNJp22+PyO g2sKAYPQ5wDkYD95Y0PaEfE0oAW/AwyVY3ZHnkrU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387404AbgDAX4C (ORCPT ); Wed, 1 Apr 2020 19:56:02 -0400 Received: from mail-lj1-f194.google.com ([209.85.208.194]:38933 "EHLO mail-lj1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732682AbgDAX4C (ORCPT ); Wed, 1 Apr 2020 19:56:02 -0400 Received: by mail-lj1-f194.google.com with SMTP id i20so1335557ljn.6 for ; Wed, 01 Apr 2020 16:56:01 -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=/BfWZS5+9as5lD6vEMwl/6xxGz06a9gloYkQ+RKeiao=; b=JfE6FWMW0WrTIHwAtwqL3bo+qhTInr5LXI005KEawz6BRmX/rJrge8UmPsiMK5pPpc uTi9rFGFrfCf6pGgobgz2x2SN1yInjn8O4MwUNtnjY4Fxxg3pNbTXYvif4DrVZeLWFYk NwMooEZifjvk8bHNwWTVKU9ykqNbijKLOcb/k= 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=/BfWZS5+9as5lD6vEMwl/6xxGz06a9gloYkQ+RKeiao=; b=YU2MYCumhCxn+JS5IPD5n29dsRIk0+otE2Pxd/IU6dXUs3YUdttyXlFgFaSCllzg/2 egu5ighlEZSAivDGLfMHKiv59w0MaVHJVW+qVpYK4t0gRgqVUv2f3Wi2yF8At7q8cb+b EhgHvszxBBXiOeI5APaWidyw9Qpv5qpe+hOkB7ha9BHg+LEmYRedZFZnaS9K6vBKO+lz AUzH6APKhic5BzF/3ivBZAr4xwzOriIAiSRv0v8aTAdfjNnqMQW20oXkVT9WWAxSksiN HbKaiB8NB01EYlCyI2nkNWdKqlHFj2kJiJpx0dr2Q9h/rRU3KN2Fwh7pkBwgDRToOhwu mNGg== X-Gm-Message-State: AGi0Pub321KyI+6BUOpYCWObDY9ePzenRjyF2QcLxjToZxj8xqdXyJde FHiPHkeiVcdVfgdF08r/d60jn6DQ380= X-Google-Smtp-Source: APiQypJ583oXCoga9l1vThnpP9mBE227RekpIi+UWs8sEri5o4eWlzjUnfisQi3B9VrbyxCjxuaQxQ== X-Received: by 2002:a05:651c:404:: with SMTP id 4mr365946lja.281.1585785359846; Wed, 01 Apr 2020 16:55:59 -0700 (PDT) Received: from mail-lj1-f171.google.com (mail-lj1-f171.google.com. [209.85.208.171]) by smtp.gmail.com with ESMTPSA id 6sm2634827lft.83.2020.04.01.16.55.58 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Apr 2020 16:55:59 -0700 (PDT) Received: by mail-lj1-f171.google.com with SMTP id k21so1376216ljh.2 for ; Wed, 01 Apr 2020 16:55:58 -0700 (PDT) X-Received: by 2002:a2e:b4cb:: with SMTP id r11mr371604ljm.201.1585785358260; Wed, 01 Apr 2020 16:55:58 -0700 (PDT) MIME-Version: 1.0 References: <20200324215049.GA3710@pi3.com.pl> <202003291528.730A329@keescook> <87zhbvlyq7.fsf_-_@x220.int.ebiederm.org> In-Reply-To: From: Linus Torvalds Date: Wed, 1 Apr 2020 16:55:42 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] signal: Extend exec_id to 64bits To: Jann Horn Cc: "Eric W. Biederman" , Alan Stern , Andrea Parri , Will Deacon , Peter Zijlstra , Boqun Feng , Nicholas Piggin , David Howells , Jade Alglave , Luc Maranget , "Paul E. McKenney" , Akira Yokosawa , Daniel Lustig , Adam Zabrocki , kernel list , Kernel Hardening , Oleg Nesterov , Andy Lutomirski , Bernd Edlinger , Kees Cook , Andrew Morton , stable Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 1, 2020 at 4:51 PM Linus Torvalds wrote: > > It's literally testing a sequence counter for equality. If you get > tearing in the high bits on the write (or the read), you'd still need > to have the low bits turn around 4G times to get a matching value. Put another way: first you'd have to work however many weeks to do 4 billion execve() calls, and then you need to hit basically a single-instruction race to take advantage of it. Good luck with that. If you have that kind of God-like capability, whoever you're attacking stands no chance in the first place. Linus