From: Laurent Vivier <laurent@vivier.eu>
To: linux-kernel@vger.kernel.org
Cc: Dmitry Safonov <dima@arista.com>,
Andrei Vagin <avagin@openvz.org>,
Eric Biederman <ebiederm@xmission.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
James Bottomley <James.Bottomley@HansenPartnership.com>,
containers@lists.linux-foundation.org,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
Laurent Vivier <laurent@vivier.eu>
Subject: [RFC v2 v2 0/1] ns: introduce binfmt_misc namespace
Date: Tue, 2 Oct 2018 12:20:53 +0200 [thread overview]
Message-ID: <20181002102054.13245-1-laurent@vivier.eu> (raw)
v2: no new namespace, binfmt_misc data are now part of
the mount namespace
I put this in mount namespace instead of user namespace
because the mount namespace is already needed and
I don't want to force to have the user namespace for that.
As this is a filesystem, it seems logic to have it here.
This allows to define a new interpreter for each new container.
But the main goal is to be able to chroot to a directory
using a binfmt_misc interpreter without being root.
I have a modified version of unshare at:
git@github.com:vivier/util-linux.git branch unshare-chroot
with some new options to unshare binfmt_misc namespace and to chroot
to a directory.
If you have a directory /chroot/powerpc/jessie containing debian for powerpc
binaries and a qemu-ppc interpreter, you can do for instance:
$ uname -a
Linux fedora28-wor-2 4.19.0-rc5+ #18 SMP Mon Oct 1 00:32:34 CEST 2018 x86_64 x86_64 x86_64 GNU/Linux
$ ./unshare --map-root-user --fork --pid \
--load-interp ":qemu-ppc:M::\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x14:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/qemu-ppc:OC" \
--root=/chroot/powerpc/jessie /bin/bash -l
# uname -a
Linux fedora28-wor-2 4.19.0-rc5+ #18 SMP Mon Oct 1 00:32:34 CEST 2018 ppc GNU/Linux
# id
uid=0(root) gid=0(root) groups=0(root),65534(nogroup)
# ls -l
total 5940
drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:58 bin
drwxr-xr-x. 2 nobody nogroup 4096 Jun 17 20:26 boot
drwxr-xr-x. 4 nobody nogroup 4096 Aug 12 00:08 dev
drwxr-xr-x. 42 nobody nogroup 4096 Sep 28 07:25 etc
drwxr-xr-x. 3 nobody nogroup 4096 Sep 28 07:25 home
drwxr-xr-x. 9 nobody nogroup 4096 Aug 12 00:58 lib
drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:08 media
drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:08 mnt
drwxr-xr-x. 3 nobody nogroup 4096 Aug 12 13:09 opt
dr-xr-xr-x. 143 nobody nogroup 0 Sep 30 23:02 proc
-rwxr-xr-x. 1 nobody nogroup 6009712 Sep 28 07:22 qemu-ppc
drwx------. 3 nobody nogroup 4096 Aug 12 12:54 root
drwxr-xr-x. 3 nobody nogroup 4096 Aug 12 00:08 run
drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:58 sbin
drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:08 srv
drwxr-xr-x. 2 nobody nogroup 4096 Apr 6 2015 sys
drwxrwxrwt. 2 nobody nogroup 4096 Sep 28 10:31 tmp
drwxr-xr-x. 10 nobody nogroup 4096 Aug 12 00:08 usr
drwxr-xr-x. 11 nobody nogroup 4096 Aug 12 00:08 var
If you want to use the qemu binary provided by your distro, you can use
--load-interp ":qemu-ppc:M::\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x14:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/bin/qemu-ppc-static:OCF"
With the 'F' flag, qemu-ppc-static will be then loaded from the main root
filesystem before switching to the chroot.
Laurent Vivier (1):
ns: add binfmt_misc to the mount namespace
fs/binfmt_misc.c | 50 +++++++++++++++++++++++++-----------------------
fs/mount.h | 8 ++++++++
fs/namespace.c | 6 ++++++
3 files changed, 40 insertions(+), 24 deletions(-)
--
2.17.1
next reply other threads:[~2018-10-02 17:04 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-02 10:20 Laurent Vivier [this message]
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
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
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