linux-kernel - Re: [PATCH v3 0/6] Composefs: an opportunistically sharing verified image filesystem

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Message-ID: <CAJfpeguq2BH_4WQDb=eGkoVGOUVhNhMRicT4b_PN-t6FTBFUoQ@mail.gmail.com>
Date:   Mon, 6 Feb 2023 20:32:16 +0100
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Alexander Larsson <alexl@...hat.com>, gscrivan@...hat.com,
        brauner@...nel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, david@...morbit.com,
        viro@...iv.linux.org.uk, Vivek Goyal <vgoyal@...hat.com>,
        Josef Bacik <josef@...icpanda.com>,
        Gao Xiang <hsiangkao@...ux.alibaba.com>,
        Jingbo Xu <jefflexu@...ux.alibaba.com>
Subject: Re: [PATCH v3 0/6] Composefs: an opportunistically sharing verified
 image filesystem

On Mon, 6 Feb 2023 at 18:16, Amir Goldstein <amir73il@...il.com> wrote:

> it's not overlay{erofs+erofs}
> it's overlay{erofs+ext4} (or another fs-verity [1] supporting fs)
> the lower layer is a mutable fs with /objects/ dir containing
> the blobs.
>
> The way to ensure the integrity of erofs is to setup dm-verity at
> erofs mount time.
>
> The way to ensure the integrity of the blobs is to store an fs-verity
> signature of each blob file in trusted.overlay.verify xattr on the
> metacopy and for overlayfs to enable fsverity on the blob file before
> allowing access to the lowerdata.
>
> At least this is my understanding of the security model.

So this should work out of the box, right?

Thanks,
Miklos