From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 4155A6B0003 for ; Sat, 17 Mar 2018 05:12:24 -0400 (EDT) Received: by mail-wr0-f198.google.com with SMTP id 65so6682856wrn.7 for ; Sat, 17 Mar 2018 02:12:24 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2a01:7a0:2:106d:700::1]) by mx.google.com with ESMTPS id 65si360292wrf.114.2018.03.17.02.12.22 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Sat, 17 Mar 2018 02:12:22 -0700 (PDT) Date: Sat, 17 Mar 2018 10:12:15 +0100 (CET) From: Thomas Gleixner Subject: Re: [PATCH 1/3] x86, pkeys: do not special case protection key 0 In-Reply-To: <20180316214656.0E059008@viggo.jf.intel.com> Message-ID: References: <20180316214654.895E24EC@viggo.jf.intel.com> <20180316214656.0E059008@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxram@us.ibm.com, dave.hansen@intel.com, mpe@ellerman.id.au, mingo@kernel.org, akpm@linux-foundation.org, shuah@kernel.org On Fri, 16 Mar 2018, Dave Hansen wrote: > > From: Dave Hansen > > mm_pkey_is_allocated() treats pkey 0 as unallocated. That is > inconsistent with the manpages, and also inconsistent with > mm->context.pkey_allocation_map. Stop special casing it and only > disallow values that are actually bad (< 0). > > The end-user visible effect of this is that you can now use > mprotect_pkey() to set pkey=0. > > This is a bit nicer than what Ram proposed because it is simpler > and removes special-casing for pkey 0. On the other hand, it does > allow applciations to pkey_free() pkey-0, but that's just a silly > thing to do, so we are not going to protect against it. What's the consequence of that? Application crashing and burning itself or something more subtle? Thanks, tglx