linux-kernel - RE: vfat: Broken case-insensitive support for UTF-8

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Message-ID: <89eba9906011446f8441090f496278d2@AcuMS.aculab.com>
Date:   Mon, 20 Jan 2020 15:07:20 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Pali Rohár' <pali.rohar@...il.com>,
        OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        Namjae Jeon <linkinjeon@...il.com>,
        "Gabriel Krisman Bertazi" <krisman@...labora.com>
Subject: RE: vfat: Broken case-insensitive support for UTF-8

From: Pali Rohár
> Sent: 20 January 2020 11:05
> On Monday 20 January 2020 13:04:42 OGAWA Hirofumi wrote:
> > Pali Rohár <pali.rohar@...il.com> writes:
> >
> > > Which means that fat_name_match(), vfat_hashi() and vfat_cmpi() are
> > > broken for vfat in UTF-8 mode.
> >
> > Right. It is a known issue.
> 
> Could be this issue better documented? E.g. in mount(8) manpage where
> are written mount options for vfat? I think that people should be aware
> of this issue when they use "utf8=1" mount option.

What happens if the filesystem has filenames that invalid UTF8 sequences
or multiple filenames that decode from UTF8 to the same 'wchar' value.
Never mind ones that are just case-differences for the same filename.

UTF8 is just so broken it should never have been allowed to become
a standard.

	David

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