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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89A5FC433EF for ; Fri, 1 Oct 2021 18:42:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C5CF6124F for ; Fri, 1 Oct 2021 18:42:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354452AbhJASnq (ORCPT ); Fri, 1 Oct 2021 14:43:46 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:35368 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S231826AbhJASn2 (ORCPT ); Fri, 1 Oct 2021 14:43:28 -0400 Received: from cwcc.thunk.org (pool-72-74-133-215.bstnma.fios.verizon.net [72.74.133.215]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 191IfVMf008675 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 1 Oct 2021 14:41:32 -0400 Received: by cwcc.thunk.org (Postfix, from userid 15806) id ABED215C34AA; Fri, 1 Oct 2021 14:41:31 -0400 (EDT) Date: Fri, 1 Oct 2021 14:41:31 -0400 From: "Theodore Ts'o" To: Shreeya Patel Cc: viro@zeniv.linux.org.uk, adilger.kernel@dilger.ca, krisman@collabora.com, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@collabora.com Subject: Re: [PATCH 2/2] fs: ext4: Fix the inconsistent name exposed by /proc/self/cwd Message-ID: References: <8402d1c99877a4fcb152de71005fa9cfb25d86a8.1632909358.git.shreeya.patel@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8402d1c99877a4fcb152de71005fa9cfb25d86a8.1632909358.git.shreeya.patel@collabora.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Sep 29, 2021 at 04:23:39PM +0530, Shreeya Patel wrote: > /proc/self/cwd is a symlink created by the kernel that uses whatever > name the dentry has in the dcache. Since the dcache is populated only > on the first lookup, with the string used in that lookup, cwd will > have an unexpected case, depending on how the data was first looked-up > in a case-insesitive filesystem. > > Steps to reproduce :- > > root@test-box:/src# mkdir insensitive/foo > root@test-box:/src# cd insensitive/FOO > root@test-box:/src/insensitive/FOO# ls -l /proc/self/cwd > lrwxrwxrwx 1 root root /proc/self/cwd -> /src/insensitive/FOO > > root@test-box:/src/insensitive/FOO# cd ../fOo > root@test-box:/src/insensitive/fOo# ls -l /proc/self/cwd > lrwxrwxrwx 1 root root /proc/self/cwd -> /src/insensitive/FOO > > Above example shows that 'FOO' was the name used on first lookup here and > it is stored in dcache instead of the original name 'foo'. This results > in inconsistent name exposed by /proc/self/cwd since it uses the name > stored in dcache. > > To avoid the above inconsistent name issue, handle the inexact-match string > ( a string which is not a byte to byte match, but is an equivalent > unicode string ) case in ext4_lookup which would store the original name > in dcache using d_add_ci instead of the inexact-match string name. I'm not sure this is a problem. /proc//cwd just needs to point at the current working directory for the process. Why do we care whether it matches the case that was stored on disk? Whether we use /src/insensitive/FOO, or /src/insensitive/Foo, or /src/insensitive/foo, all of these will reach the cwd for that process. - Ted