linux-kernel - Re: UDF filesystem image with Write-Once UDF Access Type

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Date:   Fri, 26 Jul 2019 12:44:34 -0500
From:   Steve Magnani <steve.magnani@...idescorp.com>
To:     Pali Rohár <pali.rohar@...il.com>,
        Jan Kara <jack@...e.com>, Roald Strauss <mr_lou@...fall.dk>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: UDF filesystem image with Write-Once UDF Access Type

Hi,

On 7/12/19 5:02 AM, Pali Rohár wrote:
> In my opinion without support for additional layer, kernel should treat
> UDF Write-Once Access Type as read-only mount for userspace. And not
> classic read/write mount.
>
> ...
>
> It seems that udf.ko does not support updating VAT table, so probably it
> should treat also filesystem with VAT as read-only too.
>

I thinkb085fbe2ef7fa7489903c45271ae7b7a52b0f9ab  <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/udf?h=v5.1&id=b085fbe2ef7fa7489903c45271ae7b7a52b0f9ab>, deployed in 4.20,
does both of the things you want.

One case I ran across today that Windows handles, but Linux doesn't,
is write-protection via flags in the DomainIdentifier fields of the
Logical Volume Descriptor and File Set Descriptor. Linux allows
RW mount when those are marked protected, but Windows forces RO mount.

Regards,
------------------------------------------------------------------------
  Steven J. Magnani               "I claim this network for MARS!
  www.digidescorp.com              Earthling, return my space modulator!"

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