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=-2.3 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 DC89BC43331 for ; Sat, 7 Sep 2019 09:06:44 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6C1A0208C3 for ; Sat, 7 Sep 2019 09:06:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C1A0208C3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ubuntu.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46QT7k1sGQzDr68 for ; Sat, 7 Sep 2019 19:06:42 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=ubuntu.com (client-ip=91.189.89.112; helo=youngberry.canonical.com; envelope-from=christian.brauner@ubuntu.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ubuntu.com Received: from youngberry.canonical.com (youngberry.canonical.com [91.189.89.112]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 46PTsg6BF7zDqvh for ; Fri, 6 Sep 2019 04:36:07 +1000 (AEST) 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 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) X-Mailman-Approved-At: Sat, 07 Sep 2019 18:55:13 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , Rasmus Villemoes , Alexei Starovoitov , linux-kernel@vger.kernel.org, David Howells , linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, Shuah Khan , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Tycho Andersen , Aleksa Sarai , Jiri Olsa , Alexander Shishkin , Ingo Molnar , linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-xtensa@linux-xtensa.org, Kees Cook , Arnd Bergmann , Jann Horn , linuxppc-dev@lists.ozlabs.org, Aleksa Sarai , Andy Lutomirski , Shuah Khan , Namhyung Kim , David Drysdale , Christian Brauner , "J. Bruce Fields" , linux-parisc@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-api@vger.kernel.org, Chanho Min , Jeff Layton , Oleg Nesterov , Eric Biederman , linux-alpha@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Linus Torvalds , containers@lists.linux-foundation.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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?