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Date: Wed, 20 Dec 2023 13:35:40 +0100
From: Christian Brauner <brauner@kernel.org>
To: Mimi Zohar <zohar@linux.ibm.com>
Cc: linux-unionfs@vger.kernel.org, linux-integrity@vger.kernel.org,
	linux-kernel@vger.kernel.org, Amir Goldstein <amir73il@gmail.com>,
	Seth Forshee <sforshee@kernel.org>,
	Roberto Sassu <roberto.sassu@huaweicloud.com>
Subject: Re: [PATCH v2 0/3] evm: disable EVM on overlayfs
Message-ID: <20231220-komprimieren-kooperativ-cdb5e8803ce0@brauner>
References: <20231219175206.12342-1-zohar@linux.ibm.com>
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In-Reply-To: <20231219175206.12342-1-zohar@linux.ibm.com>

On Tue, Dec 19, 2023 at 12:52:03PM -0500, Mimi Zohar wrote:
> EVM verifies the existing 'security.evm' value, before allowing it
> to be updated.  The EVM HMAC and the original file signatures contain
> filesystem specific metadata (e.g. i_ino, i_generation and s_uuid).
> 
> This poses a challenge when transitioning from the lower backing file
> to the upper backing file.
> 
> Until a complete solution is developed, disable EVM on overlayfs.
> 
> Changelog v2:
> Addressed Amir's comments:
> - Simplified security_inode_copy_up_xattr() return.
> - Identified filesystems that don't support EVM based on a new SB_I flag.

We're wasting a flag for a single filesystem but we do have enough of
them left so I think this is ok,

Reviewed-by: Christian Brauner <brauner@kernel.org>