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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 5040AC43140 for ; Thu, 5 Sep 2019 18:36:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 54E1A20828 for ; Thu, 5 Sep 2019 18:36:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390257AbfIESgE (ORCPT ); Thu, 5 Sep 2019 14:36:04 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:43350 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725290AbfIESgD (ORCPT ); Thu, 5 Sep 2019 14:36:03 -0400 Received: from [46.114.37.115] (helo=localhost) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1i5wbZ-0006Ee-52; Thu, 05 Sep 2019 18:35:37 +0000 Date: Thu, 5 Sep 2019 20:35:32 +0200 From: Christian Brauner To: Al Viro Cc: Aleksa Sarai , Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Ingo Molnar , Peter Zijlstra , Christian Brauner , Rasmus Villemoes , Eric Biederman , Andy Lutomirski , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , David Drysdale , Chanho Min , Oleg Nesterov , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Aleksa Sarai , Linus Torvalds , containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org, sparclinux@vger.kernel.org Subject: Re: [PATCH v12 01/12] lib: introduce copy_struct_{to,from}_user helpers Message-ID: <20190905183532.GA25049@localhost> References: <20190904201933.10736-1-cyphar@cyphar.com> <20190904201933.10736-2-cyphar@cyphar.com> <20190905180750.GQ1131@ZenIV.linux.org.uk> <20190905182303.7f6bxpa2enbgcegv@wittgenstein> <20190905182801.GR1131@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190905182801.GR1131@ZenIV.linux.org.uk> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Thu, Sep 05, 2019 at 07:28:01PM +0100, Al Viro wrote: > On Thu, Sep 05, 2019 at 08:23:03PM +0200, Christian Brauner wrote: > > > Because every caller of that function right now has that limit set > > anyway iirc. So we can either remove it from here and place it back for > > the individual callers or leave it in the helper. > > Also, I'm really asking, why not? Is it unreasonable to have an upper > > bound on the size (for a long time probably) or are you disagreeing with > > PAGE_SIZE being used? PAGE_SIZE limit is currently used by sched, perf, > > bpf, and clone3 and in a few other places. > > For a primitive that can be safely used with any size (OK, any within > the usual 2Gb limit)? Why push the random policy into the place where > it doesn't belong? Ah, the "not in the helper part" makes sense. As long as leave the check for the callers themselves. > > Seriously, what's the point? If they want to have a large chunk of > userland memory zeroed or checked for non-zeroes - why would that > be a problem?