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

From: Roberto Sassu
Date: Fri May 10 2019 - 02:57:54 EST

On 5/9/2019 8:34 PM, Rob Landley wrote:
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.

This can be modified. Now I allocate the memory necessary for the path
and all xattrs of a file (max: .xattr-list size - 10 bytes). I could
process each xattr individually (max: 255 + 1 + 65536 bytes).

The difference with another proposal
( 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.

Can you be more specific?




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