From: Vivek Goyal <vgoyal@redhat.com>
To: Piotr Jurkiewicz <piotr.jerzy.jurkiewicz@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
kvm@vger.kernel.org, miklos@szeredi.hu, stefanha@redhat.com,
dgilbert@redhat.com, sweil@redhat.com, swhiteho@redhat.com
Subject: Re: [PATCH 00/52] [RFC] virtio-fs: shared file system for virtual machines
Date: Wed, 12 Dec 2018 16:25:53 -0500 [thread overview]
Message-ID: <20181212212553.GB23229@redhat.com> (raw)
In-Reply-To: <dc2e6e0f-ab00-a114-0fc1-e787293a73cf@gmail.com>
On Wed, Dec 12, 2018 at 06:07:40PM +0100, Piotr Jurkiewicz wrote:
> Currently, virtio-9p cannot be used with overlayfs in order to obtain
> Docker-like experience (but with separate kernel) because of file attributes
> problems. I wrote an email about that to qemu-devel almost year ago, but it
> received no attention (I attach its contents below.).
>
> Will virtio-fs avoid these problems? I assume it will be transparent from
> the point of view of file attributes, and not enforce any kind of security
> filtering?
Hi Piotr,
So you want to use virtio-fs as upper/ layer of a overlay filesystem
inside guest? Interesting. I have not tried that.
As of now I think we are not doing any filtering of file attributes
and it might just work. Give it a try. Having said that, I suspect
that security model of virtio-fs most likely will evolve.
Thanks
Vivek
>
> Piotr Jurkiewicz
>
> ----
>
> 1. Upper filesystem must support the creation of trusted.* extended
> attributes.
>
> 9pfs has support for getting/setting xattrs, but calls operating on
> attributes other than user.* and system.posix_acl_* are dropped.
>
> 2. Upper filesystem must provide valid d_type in readdir responses.
>
> This works, but only in case of 'passtrough' and 'none' security models. In
> the case of 'mapped-xattr' and 'mapped-file' models, d_type is being zeroed
> to DT_UNKNOWN during readdir() call.
>
> All these limitations can be resolved pretty easily, but requires some
> design decisions. I can prepare appropriate patches.
>
> Ad. 1.
>
> Why are operations on attributes other than than user.* and
> system.posix_acl_* forbidden? Is this due to security reasons?
>
> If so, can we map all of them to user.virtfs namespace, similarly as
> system.posix_acl_* are being mapped to user.virtfs.system.posix_acl_* in
> 'mapping' mode already? This way any trusted/security/system attributes will
> be effective only when mounted via virtfs inside VM.
>
> Ad. 2.
>
> local_readdir() can fill entry->d_type with the right DT_* value by
> obtaining file type from mapping and translating it with IFTODT() macro.
> This would, however, require reading 'user.virtfs.mode' for each direntry
> during readdir() call, what can affect performance. If so, this behavior
> would probably need to be controlled with some runtime option.
>
> 'mapped-xattr' and 'mapped-file' models are essential for running qemu with
> overlayfs as non-root, because overlayfs creates device nodes, what is
> possible for unprivileged user only with these models.
next prev parent reply other threads:[~2018-12-12 21:25 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-12 17:07 [PATCH 00/52] [RFC] virtio-fs: shared file system for virtual machines Piotr Jurkiewicz
2018-12-12 21:25 ` Vivek Goyal [this message]
-- strict thread matches above, loose matches on Subject: below --
2018-12-10 17:12 Vivek Goyal
2018-12-11 12:54 ` Stefan Hajnoczi
2018-12-12 20:30 ` Konrad Rzeszutek Wilk
2018-12-12 21:22 ` Vivek Goyal
2019-02-12 15:56 ` Aneesh Kumar K.V
2019-02-12 18:57 ` Vivek Goyal
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181212212553.GB23229@redhat.com \
--to=vgoyal@redhat.com \
--cc=dgilbert@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=piotr.jerzy.jurkiewicz@gmail.com \
--cc=stefanha@redhat.com \
--cc=sweil@redhat.com \
--cc=swhiteho@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).