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=-0.8 required=3.0 tests=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 35171C43331 for ; Wed, 1 Apr 2020 23:56:19 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 86898206D3 for ; Wed, 1 Apr 2020 23:56:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="JfE6FWMW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 86898206D3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18364-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 25857 invoked by uid 550); 1 Apr 2020 23:56:13 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 25837 invoked from network); 1 Apr 2020 23:56:12 -0000 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=BVpbgCdJbllnSY59Z25HuVi0hwF+hYuR6UKWO0hC2g9CXxa9idczIDwSba8LZjyHeA fBc+SnLezmiEhjwsX6boyacyE/MAGJze8pnCmdHbNKda0lnAYjNZhZgbOB5HfvVonDkg dmxt12Y5EEQxV4e67CUizmLrw3ycxKJP8bn+0hItdohx8kDE1ZApvoj54IepEemFY3vt LmZs9VY/U5AbSw3rJs7JHF0oLcXiOAw12CktsE409rPGCejH7eHxmctnLN1yVB+m6mMX 5bS4otwF8TTXhQ9PDFP9YneKYfxgJwjcaYyoeKIYyhsrLoMCa7uFJpZktiY5SMZatvQT 6kag== X-Gm-Message-State: AGi0PuaF8EOT6EKEIJkjIvLKofjPNHUBm5i+tc8T+x5AghfUP9qESQGi yUgA0UnXNfT2LY+9u5Dgd0p7uz0VZRY= X-Google-Smtp-Source: APiQypJi20g7wYESJp1kDEQeKKcBIbv8GQ7gDuC6sNUfWlOlDuoDzV6kANwvdp4EMT4wZp3pXXUUnw== X-Received: by 2002:a2e:9718:: with SMTP id r24mr326765lji.287.1585785360505; Wed, 01 Apr 2020 16:56:00 -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" 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