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 1D41FC433EF for ; Wed, 22 Sep 2021 19:58:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EF6D7611C4 for ; Wed, 22 Sep 2021 19:58:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237302AbhIVUAP (ORCPT ); Wed, 22 Sep 2021 16:00:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230384AbhIVUAN (ORCPT ); Wed, 22 Sep 2021 16:00:13 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 58B7DC061574 for ; Wed, 22 Sep 2021 12:58:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=zR61vV1oybrOw3cyGY8F42IMCGnnL9DJ5uQe7oNLLZ0=; b=GWesiIwwuZoSo0GUVbwI/18JuB ngeTKQ8CHD4cT/52SQoaWaKG8T4IaOdBMMSBtSTJ+HdCQnupJkjpvrcIbIowx6O4evWoP5kZ1vf0n pU7Q6jlU8Ad6fdS+izfz+kE0wL9vYivvba9ivJX5hi7fFThSJpn2nUE7dSRmqBq//5clvj7KwQMaX wVU3cnzm6GcFIXlNlh3Endf9lyA5qdjsJMYsL2KTLHC/vbIUmXZoHYyigpmGgcIa5i2lclgPEmXqv 4N/mJrlbpKz28z5TLpHpeuPL+b6QmNeN/cwCNtwPTvzy0ZyWzY2jjmwWzT56mtrJ5rQuC6h0R8jOo 3AlxbuVw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mT8Ip-0055N5-3G; Wed, 22 Sep 2021 19:53:31 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id B4EDF3001CD; Wed, 22 Sep 2021 21:53:07 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 570E82D7CF34A; Wed, 22 Sep 2021 21:53:07 +0200 (CEST) Date: Wed, 22 Sep 2021 21:53:07 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: David Hildenbrand , Peter Collingbourne , Catalin Marinas , Will Deacon , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Thomas Gleixner , Andy Lutomirski , Kees Cook , Andrew Morton , Masahiro Yamada , Sami Tolvanen , YiFei Zhu , Colin Ian King , Mark Rutland , Frederic Weisbecker , Viresh Kumar , Andrey Konovalov , Gabriel Krisman Bertazi , Balbir Singh , Chris Hyser , Daniel Vetter , Chris Wilson , Arnd Bergmann , Dmitry Vyukov , Christian Brauner , "Eric W. Biederman" , Alexey Gladkov , Ran Xiaokai , Xiaofeng Cao , Cyrill Gorcunov , Thomas Cedeno , Marco Elver , Alexander Potapenko , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Evgenii Stepanov Subject: Re: [PATCH] kernel: introduce prctl(PR_LOG_UACCESS) Message-ID: References: <20210922061809.736124-1-pcc@google.com> <29f1822d-e4cd-eedb-bea8-619db1d56335@redhat.com> <20210922152250.4e7c869a@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210922152250.4e7c869a@gandalf.local.home> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 22, 2021 at 03:22:50PM -0400, Steven Rostedt wrote: > On Wed, 22 Sep 2021 19:46:47 +0200 > David Hildenbrand wrote: > > > > All signals except SIGKILL and SIGSTOP are masked for the interval > > > between the prctl() and the next syscall in order to prevent handlers > > > for intervening asynchronous signals from issuing syscalls that may > > > cause uaccesses from the wrong syscall to be logged. > > > > Stupid question: can this be exploited from user space to effectively > > disable SIGKILL for a long time ... and do we care? > > I first misread it too, but then caught my mistake reading it a second > time. It says "except SIGKILL". So no, it does not disable SIGKILL. Disabling SIGINT might already be a giant nuisance. Letting through SIGSTOP but not SIGCONT seems awkward. Blocking SIGTRAP seems like a bad idea too. Blocking SIGBUS as delivered by #MC will be hillarious.