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=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 426ADC433ED for ; Thu, 8 Apr 2021 08:46:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 21A0361164 for ; Thu, 8 Apr 2021 08:46:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229689AbhDHIqJ (ORCPT ); Thu, 8 Apr 2021 04:46:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229566AbhDHIqJ (ORCPT ); Thu, 8 Apr 2021 04:46:09 -0400 Received: from mail-yb1-xb2b.google.com (mail-yb1-xb2b.google.com [IPv6:2607:f8b0:4864:20::b2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5911DC061760; Thu, 8 Apr 2021 01:45:58 -0700 (PDT) Received: by mail-yb1-xb2b.google.com with SMTP id z1so1800874ybf.6; Thu, 08 Apr 2021 01:45:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=99J/CBzF8eeODcwTLJG1kD3GoFOA/YtJT+K2uJ6P1yo=; b=bhM38B4AF1UqtXySCz92Ptq2REVaikD5Y5yxUaKO7BUjux6HIhe0wBLIfObYSFXvuq 81azzZAW/btmRfS9dHpCWQJVsbji6UpeXiG95l7EfqecBSizs9RuBnLsNEzGwxw/U+xz KrvcOg0PKpDE/SB0o4oflbv8gxpW1Klpcs6Rq41qn7bLBFZ23mZvbUQfwSWryX1B+No5 W3HroZu5wniL9vV5kQb20cpgqXyNUfX6xqR9YtpkLT2rXIe29+d5b/hxHoPLvR0Z5DoI WjHgZ6jsEOBgIGPOTh4FCuwaXJEgOSx+/Q4yBiEv+tdtPrSKeB5AllizDt31Z/TC+lwN yDEQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=99J/CBzF8eeODcwTLJG1kD3GoFOA/YtJT+K2uJ6P1yo=; b=QvRTyDmzX3T/ky4EnpyQwsEL9igepwYbPeXFvoFrUj/M5UBW9HFg1ta4UsnR+RxiTU zFn9IY2Bzhqp9cyHofQjPf2dAdUDKpBby0sPMJ7FKzsTl3u8rV2u+ZBbmI5ugQqVVKBz ENttA5ylj/KSIWDuLHgVFet1QXvD1QmUm7CRidhrFIgd+dTqJYXvZ3CfjH92WMNaa3gy kJ5llj8ZRQwXifTLdtzmuwK7ZLIi+12OaW4MENItWf/96bcKprLn3ahqVVCIn7FAYzaK sOXfphQDesHXlwNLGEYLcm4YYTreIBf4LP4hN13lZ8e9v5FMmiEtfq9xqeSviJuF5WU6 SAkw== X-Gm-Message-State: AOAM533kuNfvpstZ4qa1g4tj+oThc/BdtNqm/9ji+rwi9ZS2PQpHEhc4 c6pKyfsav2j3l7T52gM5JT918BP9Y/Md42o0rOA= X-Google-Smtp-Source: ABdhPJzQ91IitgARZIRhXoXa3dYqesHpWzFqneoB2jN1/OpeIqtlUH4dc7cb2t9aWQqxJq+BhoJpZQo1w6AbqJ2asK8= X-Received: by 2002:a25:a087:: with SMTP id y7mr9873697ybh.167.1617871557515; Thu, 08 Apr 2021 01:45:57 -0700 (PDT) MIME-Version: 1.0 References: <20210330055957.3684579-1-dkadashev@gmail.com> <20210330055957.3684579-2-dkadashev@gmail.com> <20210330071700.kpjoyp5zlni7uejm@wittgenstein> In-Reply-To: <20210330071700.kpjoyp5zlni7uejm@wittgenstein> From: Dmitry Kadashev Date: Thu, 8 Apr 2021 15:45:46 +0700 Message-ID: Subject: Re: [PATCH v3 1/2] fs: make do_mkdirat() take struct filename To: Christian Brauner Cc: Jens Axboe , Alexander Viro , Pavel Begunkov , linux-fsdevel@vger.kernel.org, io-uring Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Mar 30, 2021 at 2:17 PM Christian Brauner wrote: > The only thing that is a bit unpleasant here is that this change > breaks the consistency between the creation helpers: > > do_mkdirat() > do_symlinkat() > do_linkat() > do_mknodat() > > All but of them currently take > const char __user *pathname > and call > user_path_create() > with that do_mkdirat() change that's no longer true. One of the major > benefits over the recent years in this code is naming and type consistency. > And since it's just matter of time until io_uring will also gain support > for do_{symlinkat,linkat,mknodat} I would think switching all of them to > take a struct filename > and then have all do_* helpers call getname() might just be nicer in the > long run. So, I've finally got some time to look into this. do_mknodat() and do_symlinkat() are easy. But do_linkat() is more complicated, I could use some hints as to what's the reasonable way to implement the change. The problem is linkat() requires CAP_DAC_READ_SEARCH capability if AT_EMPTY_PATH flag is passed. Right now do_linkat checks the capability before calling getname_flags (essentially). If do_linkat is changed to accept struct filename then there is no bulletproof way to force CAP_DAC_READ_SEARCH presence (e.g. if for whatever reason AT_EMPTY_PATH is not in flags passed to do_linkat). Also, it means that the caller is responsible to process AT_EMPTY_PATH in the first place, which means logic duplication. Any ideas what's the best way to approach this? Thanks. -- Dmitry Kadashev