linux-kernel - Re: [PATCH 4/5] evm: Use the real inode's metadata to calculate metadata hash

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Date: Fri, 2 Feb 2024 18:17:32 +0200
From: Amir Goldstein <amir73il@...il.com>
To: Stefan Berger <stefanb@...ux.ibm.com>
Cc: linux-integrity@...r.kernel.org, linux-security-module@...r.kernel.org, 
	linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com, zohar@...ux.ibm.com, 
	roberto.sassu@...wei.com, miklos@...redi.hu
Subject: Re: [PATCH 4/5] evm: Use the real inode's metadata to calculate
 metadata hash

> The odd thing is my updated test case '2' seems to indicate that
> everything already works as expected with CONFIG_OVERLAY_FS_METACOPY=y.
> After causing copy-up of metadata changes to the file content on the
> lower layer still cause permission error to file execution on the
> overlay layer and after restoring the file content on the lower the file
> on the overlay again runs as expected. The file content change + copy-up
> of file content also has completely decoupled the lower file from the
> file on the overlay and changes to the file on the lower cause no more
> file execution rejections on the overlay.
>

Sorry, you lost me.
The combination of IMA+EVM+OVL must be too complicated to
explain in plain language without an explicit test spelled out...

When you write "The file content change + copy-up of file content also
has completely decoupled the lower file from the file on the overlay",
what do you mean by "copy up of the file content"?
Why was the file content copied up?
I was asking about use case that only metadata was copied up but
lower file content, which is still the content of the ovl file was changed
underneath ovl - this case does not cause data content to be copied up.

I don't think we understand each other.

Thanks,
Amir.