From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1757292AbdELISV (ORCPT <rfc822;w@1wt.eu>);
        Fri, 12 May 2017 04:18:21 -0400
Received: from zeniv.linux.org.uk ([195.92.253.2]:34016 "EHLO
        ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1756855AbdELISR (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 12 May 2017 04:18:17 -0400
Date: Fri, 12 May 2017 09:16:58 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Christoph Hellwig <hch@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@kernel.org>,
        Andy Lutomirski <luto@kernel.org>, Greg KH <greg@kroah.com>,
        Thomas Garnier <thgarnie@google.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        David Howells <dhowells@redhat.com>,
        =?iso-8859-1?Q?Ren=E9?= Nyffenegger <mail@renenyffenegger.ch>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Pavel Tikhomirov <ptikhomirov@virtuozzo.com>,
        Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
        Paolo Bonzini <pbonzini@redhat.com>, Rik van Riel <riel@redhat.com>,
        Kees Cook <keescook@chromium.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Brian Gerst <brgerst@gmail.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Russell King <linux@armlinux.org.uk>,
        Will Deacon <will.deacon@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Mark Rutland <mark.rutland@arm.com>, James Morse <james.morse@arm.com>,
        linux-s390 <linux-s390@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address
 limit before returning to user-mode
Message-ID: <20170512081658.GR390@ZenIV.linux.org.uk>
References: <CAJcbSZGQsRVg3QZ9QfLn2HBC+RP-7fUTab0bYDJ455d8y8GyNw@mail.gmail.com>
 <20170508073352.caqe3fqf7nuxypgi@gmail.com>
 <20170508124621.GA20705@kroah.com>
 <20170509064522.anusoikaalvlux3w@gmail.com>
 <20170509085659.GA32555@infradead.org>
 <CALCETrUh8NO2scaqEM48K70Fo2+V3=Cpyk4JurCDiCYp4nm_+g@mail.gmail.com>
 <20170512070012.7dysuhbkcas7ibaj@gmail.com>
 <20170512071549.GP390@ZenIV.linux.org.uk>
 <CAK8P3a2ynRObJLn2Hh2r9_2k5+O08jErPC_UnnDmemd1jXsnkw@mail.gmail.com>
 <20170512081126.GA7188@infradead.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170512081126.GA7188@infradead.org>
User-Agent: Mutt/1.8.0 (2017-02-23)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, May 12, 2017 at 01:11:26AM -0700, Christoph Hellwig wrote:

> But it won't help against exploits modifying addr_limit manually.

Or the ones setting current->cred to that of init.  Your point being?