linux-kernel - Re: [PATCH v2 0/3] initramfs: add support for xattrs in the initial ram disk

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Date:   Thu, 9 May 2019 13:34:13 -0500
From:   Rob Landley <rob@...dley.net>
To:     Roberto Sassu <roberto.sassu@...wei.com>, viro@...iv.linux.org.uk
Cc:     linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, initramfs@...r.kernel.org,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, zohar@...ux.vnet.ibm.com,
        silviu.vlasceanu@...wei.com, dmitry.kasatkin@...wei.com,
        takondra@...co.com, kamensky@...co.com, hpa@...or.com,
        arnd@...db.de, james.w.mcmechan@...il.com
Subject: Re: [PATCH v2 0/3] initramfs: add support for xattrs in the initial
 ram disk

On 5/9/19 6:24 AM, Roberto Sassu wrote:
> This patch set aims at solving the following use case: appraise files from
> the initial ram disk. To do that, IMA checks the signature/hash from the
> security.ima xattr. Unfortunately, this use case cannot be implemented
> currently, as the CPIO format does not support xattrs.
> 
> This proposal consists in marshaling pathnames and xattrs in a file called
> .xattr-list. They are unmarshaled by the CPIO parser after all files have
> been extracted.

So it's in-band signalling that has a higher peak memory requirement.

> The difference with another proposal
> (https://lore.kernel.org/patchwork/cover/888071/) is that xattrs can be
> included in an image without changing the image format, as opposed to
> defining a new one. As seen from the discussion, if a new format has to be
> defined, it should fix the issues of the existing format, which requires
> more time.

So you've explicitly chosen _not_ to address Y2038 while you're there.

Rob