Re: overlayfs access checks on underlying layers

From: Miklos Szeredi <miklos@szeredi.hu>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>,
	Ondrej Mosnacek <omosnace@redhat.com>,
	"J. Bruce Fields" <bfields@fieldses.org>,
	Mark Salyzyn <salyzyn@android.com>,
	Paul Moore <paul@paul-moore.com>,
	linux-kernel@vger.kernel.org,
	overlayfs <linux-unionfs@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org, selinux@vger.kernel.org,
	Daniel J Walsh <dwalsh@redhat.com>
Subject: Re: overlayfs access checks on underlying layers
Date: Tue, 4 Dec 2018 16:31:09 +0100	[thread overview]
Message-ID: <CAJfpegtFVvq286HAorGLg6ywMsfs51KqaQwFkcuV7Dtu8TLaLg@mail.gmail.com> (raw)
In-Reply-To: <20181204152248.GB21509@redhat.com>

On Tue, Dec 4, 2018 at 4:22 PM Vivek Goyal <vgoyal@redhat.com> wrote:

> Having said that, this still create little anomaly when mknod to client
> is not allowed on context label. So a device file, which is on lower
> and client can not open it for read/write on host, it can now be opened
> for read/write because mounter will allow access. So why it is different
> that regular copy up. Well, in regular copy up, we created a copy of
> the original object and allowed writing to that object (cp --preserve=all)
> model. But in case of device file, writes will go to same original
> object. (And not a separate copy).

That's true.

In that sense copy up of special file should result in upper having
the same label as of lower, right?

Thanks,
Miklos