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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 7B206C43603 for ; Tue, 17 Dec 2019 04:22:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4688E2146E for ; Tue, 17 Dec 2019 04:22:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=szeredi.hu header.i=@szeredi.hu header.b="nfWq8THx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727452AbfLQEWb (ORCPT ); Mon, 16 Dec 2019 23:22:31 -0500 Received: from mail-io1-f67.google.com ([209.85.166.67]:44620 "EHLO mail-io1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726296AbfLQEWb (ORCPT ); Mon, 16 Dec 2019 23:22:31 -0500 Received: by mail-io1-f67.google.com with SMTP id b10so9474162iof.11 for ; Mon, 16 Dec 2019 20:22:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=keSgIbSHJC75F2tcCTcdvMMClu3dUDODUJgUvRgq/Q4=; b=nfWq8THxKflsuQnA3Xr6tSm1cQ+bf2FbIlVmRYJ70h0dRDqxvS6Wd9V9l+9w7bfVgh knvfkPlbAsgA2EMV0tqPNVQRf6Z8/cx4RlXP/dgEDC4DTSRn8IFNAAGZH83S+LZgq4y3 pOCDa1ev49hHwFbIWIsd27FuDVwkiOFv3yI/o= 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=keSgIbSHJC75F2tcCTcdvMMClu3dUDODUJgUvRgq/Q4=; b=MU/QEU8quL/ACUUuMhSmcXrU2sRniVsrSyisyx3pISXdWwzx3ccsiMxaCTZk0SBQQS xqgKlZBmr8bftkOOHECjCuHSI/Z5NLnYM9UtEmeXQFrWCYhhdhtixZRzk3svtcM1Wmu7 bFJTlbGiC6obwIIDZE5o/bnthIgGaQuJX9eCEXBPqAGH04tYnYT/1glMZ7bN6AXn58xJ hOODCQZmlD/1AWJ8dd8VZBf6In9Y013jZDxOxzx9sasU58bqonBRGKaUf3NaULeiudzC YmI7V/Al+49OU5nqwvmqIoFGKnJwftmXeX9JE7xTq9DF3heq1/s4R0rKj1N7vYRaYnfU PByw== X-Gm-Message-State: APjAAAVd6Bqo89606LL8ZXhhO8C1MTPtH2ZFaboLwpeAbnWWctUdWewZ 2RGLH0Vi4i7g2KcqLxnYZaa4cFvlABJs49OjQV/Lfw== X-Google-Smtp-Source: APXvYqy4NjiwAH//btd3CRVvOmWfV/UyzeyDT2aKGrfCpGjD2ZTP/coIOrKvfnCUOgFR0cLA0ZuVpdDe0uBeyumlEbo= X-Received: by 2002:a5d:9b04:: with SMTP id y4mr2168997ion.212.1576556550745; Mon, 16 Dec 2019 20:22:30 -0800 (PST) MIME-Version: 1.0 References: <20191128155940.17530-1-mszeredi@redhat.com> <20191128155940.17530-9-mszeredi@redhat.com> <20191217035144.GU4203@ZenIV.linux.org.uk> In-Reply-To: <20191217035144.GU4203@ZenIV.linux.org.uk> From: Miklos Szeredi Date: Tue, 17 Dec 2019 05:22:20 +0100 Message-ID: Subject: Re: [PATCH 08/12] vfs: allow unprivileged whiteout creation To: Al Viro Cc: Miklos Szeredi , linux-fsdevel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Dec 17, 2019 at 4:51 AM Al Viro wrote: > > On Thu, Nov 28, 2019 at 04:59:36PM +0100, Miklos Szeredi wrote: > > Whiteouts are special, but unlike real device nodes they should not require > > privileges to create. > > More detailed analysis, please. Maybe I'm missing something obvious, > but I don't see off-hand why it's safe. The general concern with device nodes is that opening them can have side effects. The kernel already avoids zero major, so opening will result in ENODEV, but the patch also makes sure that registering a device with 0/0 number is forbidden (fs/char_dev.c). Thanks, Miklos