archive mirror
 help / color / mirror / Atom feed
From: Jann Horn <>
To: "Eric W. Biederman" <>
Cc: Laurent Vivier <>,
	kernel list <>,, Andrei Vagin <>,
	Al Viro <>,
	James Bottomley <>,,,
	Linux API <>
Subject: Re: [RFC v2 v2 1/1] ns: add binfmt_misc to the mount namespace
Date: Wed, 3 Oct 2018 21:26:56 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, Oct 3, 2018 at 8:07 AM Eric W. Biederman <> wrote:
> Laurent Vivier <> writes:
> > This patch allows to have a different binftm_misc configuration
> > in each container we mount binfmt_misc filesystem with mount namespace
> > enabled.
> >
> > A container started without the CLONE_NEWNS will use the host binfmt_misc
> > configuration, otherwise the container starts with an empty binfmt_misc
> > interpreters list.
> >
> > For instance, using "unshare" we can start a chroot of an another
> > architecture and configure the binfmt_misc interpreted without being root
> > to run the binaries in this chroot.
> A couple of things.
> As has already been mentioned on your previous version anything that
> comes through the filesystem interface needs to lookup up the local
> binfmt context not through current but through file->f_dentry->d_sb.
> AKA the superblock of the mounted filesystem.

Something else: bm_register_write() currently calls into open_exec(),
which uses the credentials of current. That's not really allowed in
this context - but so far, it's not a big deal because only
init-namespace root can reach this code. Before you expose this stuff
to unprivileged userspace, this needs to get fixed; perhaps by
wrapping the open_exec() call in override_creds(file->f_cred) and

  reply	other threads:[~2018-10-04  2:17 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-02 10:20 [RFC v2 v2 0/1] ns: introduce binfmt_misc namespace Laurent Vivier
2018-10-02 10:20 ` [RFC v2 v2 1/1] ns: add binfmt_misc to the mount namespace Laurent Vivier
2018-10-03  6:07   ` Eric W. Biederman
2018-10-03 19:26     ` Jann Horn [this message]
2018-10-02 16:13 ` [RFC v2 v2 0/1] ns: introduce binfmt_misc namespace James Bottomley
2018-10-02 16:47   ` Laurent Vivier
2018-10-03 10:13     ` James Bottomley

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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='' \ \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [RFC v2 v2 1/1] ns: add binfmt_misc to the mount namespace' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

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).