From: Eric Biggers <ebiggers@kernel.org>
To: Alexander Larsson <alexl@redhat.com>
Cc: miklos@szeredi.hu, linux-unionfs@vger.kernel.org,
amir73il@gmail.com, tytso@mit.edu, fsverity@lists.linux.dev
Subject: Re: [PATCH v2 4/6] ovl: Add framework for verity support
Date: Sun, 14 May 2023 23:00:08 -0700 [thread overview]
Message-ID: <20230515060008.GA15871@sol.localdomain> (raw)
In-Reply-To: <CAL7ro1EaqFcS5sRAAJLWuiy4OHEP8KGXTm5T-LRh09XSrnav5A@mail.gmail.com>
On Mon, May 15, 2023 at 07:44:13AM +0200, Alexander Larsson wrote:
> On Sun, May 14, 2023 at 9:22 PM Eric Biggers <ebiggers@kernel.org> wrote:
> >
> > On Wed, May 03, 2023 at 10:51:37AM +0200, Alexander Larsson wrote:
> > > +- "require":
> > > + Same as "on", but additionally all metacopy files must specify a
> > > + verity xattr. This means metadata copy up will only be used if
> > > + the data file has fs-verity enabled, otherwise a full copy-up is
> > > + used.
> >
> > The second sentence makes it sound like an attacker can inject arbitrary data
> > just by replacing a data file with one that doesn't have fsverity enabled.
> >
> > I really hope that's not the case?
> >
> > I *think* there is a subtlety here involving "metacopy files" that were created
> > ahead of time by the user, vs. being generated by overlayfs. But it's not
> > really explained.
>
> I'm not sure what you mean here? When you say "replacing a data file",
> do you mean "changing the content of the lowerdir"?
Yes. Specifically the data-only lowerdir.
> Because if you can just change lowerdir content then you can make users of the
> overlayfs mount read whatever data you want (independent of metacopy or any of
> this).
But isn't preventing that the whole point of your feature?
What am I missing?
- Eric
next prev parent reply other threads:[~2023-05-15 6:00 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-03 8:51 [PATCH v2 0/6] ovl: Add support for fs-verity checking of lowerdata Alexander Larsson
2023-05-03 8:51 ` [PATCH v2 1/6] fsverity: Export fsverity_get_digest Alexander Larsson
2023-05-03 8:51 ` [PATCH v2 2/6] ovl: Break out ovl_e_path_real() from ovl_i_path_real() Alexander Larsson
2023-05-03 8:51 ` [PATCH v2 3/6] ovl: Break out ovl_e_path_lowerdata() from ovl_path_lowerdata() Alexander Larsson
2023-05-03 8:51 ` [PATCH v2 4/6] ovl: Add framework for verity support Alexander Larsson
2023-05-03 11:51 ` Amir Goldstein
2023-05-14 19:22 ` Eric Biggers
2023-05-15 5:44 ` Alexander Larsson
2023-05-15 6:00 ` Eric Biggers [this message]
2023-05-15 6:46 ` Alexander Larsson
2023-05-03 8:51 ` [PATCH v2 5/6] ovl: Validate verity xattr when resolving lowerdata Alexander Larsson
2023-05-03 15:35 ` Amir Goldstein
2023-05-14 19:16 ` Eric Biggers
2023-05-14 21:00 ` Amir Goldstein
2023-05-15 6:14 ` Alexander Larsson
2023-06-09 13:03 ` Amir Goldstein
2023-06-10 15:02 ` Alexander Larsson
2023-06-11 11:20 ` Amir Goldstein
2023-06-12 10:32 ` Alexander Larsson
2023-06-16 5:07 ` Amir Goldstein
2023-06-16 5:24 ` Eric Biggers
2023-06-16 5:55 ` Amir Goldstein
2023-06-16 7:50 ` Alexander Larsson
2023-06-16 8:12 ` Amir Goldstein
2023-06-16 8:39 ` Alexander Larsson
2023-06-16 9:27 ` Amir Goldstein
2023-06-16 11:33 ` Alexander Larsson
2023-06-16 12:24 ` Amir Goldstein
2023-06-16 12:28 ` Miklos Szeredi
2023-06-16 13:14 ` Gao Xiang
2023-05-15 6:12 ` Alexander Larsson
2023-05-03 8:51 ` [PATCH v2 6/6] ovl: Handle verity during copy-up Alexander Larsson
2023-05-03 15:33 ` Amir Goldstein
2023-05-14 19:09 ` [PATCH v2 0/6] ovl: Add support for fs-verity checking of lowerdata Eric Biggers
2023-05-14 21:25 ` Amir Goldstein
2023-05-14 22:19 ` Gao Xiang
2023-05-15 5:55 ` Alexander Larsson
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