[PATCH 0/7] Initial support for user namespace owned mounts

Seth Forshee
2015-07-15T19:47:18Z

These are the first in a larger set of patches that I've been working on
(with help from Eric Biederman) to support mounting ext4 and fuse
filesystems from within user namespaces. I've pushed the full series to:

git://kernel.ubuntu.com/sforshee/linux.git userns-mounts

Taking the series as a whole, the strategy is to handle as much of the
heavy lifting as possible in the vfs so the filesystems don't have to
handle weird edge cases. If you look at the full series you'll find that
the changes in ext4 to support user namespace mounts turn out to be
fairly minimal (fuse is a bit more complicated though as it must deal
with translating ids for a userspace process which is running in pid and
user namespaces).

The patches I'm sending today lay some of the groundwork in the vfs and
related code. They fall into two broad groups:

1. Patches 1-2 add s_user_ns and simplify MNT_NODEV handling. These are
pretty straightforward, and Eric has expressed interest in merging
these patches soon. Note that patch 2 won't apply cleanly without
Eric's noexec patches for proc and sys [1].

2. Patches 2-7 tighten down security for mounts with s_user_ns !=
&init_user_ns. This includes updates to how file caps and suid are
handled and LSM updates to ignore security labels on superblocks
from non-init namespaces.

The LSM changes in particular may not be optimal, as I don't have a
lot of familiarity with this code, so I'd be especially appreciative
of review of these changes and suggestions on how to improve them.

Subsequent patches will update the vfs for id translation, handling
various corner cases, giving privileges to the user namsepace which owns
a superblock, and finally supporting user namespace mounts for ext4 and
fuse.

Thanks,
Seth

[1] http://lkml.kernel.org/r/87mvz4yomp.fsf_-_@x220.int.ebiederm.org

Andy Lutomirski (1):
fs: Treat foreign mounts as nosuid

Eric W. Biederman (1):
userns: Simpilify MNT_NODEV handling.

Seth Forshee (5):
fs: Add user namesapace member to struct super_block
fs: Ignore file caps in mounts from other user namespaces
security: Restrict security attribute updates for userns mounts
selinux: Ignore security labels on user namespace mounts
smack: Don't use security labels for user namespace mounts

fs/block_dev.c | 2 +-
fs/exec.c | 2 +-
fs/namei.c | 9 ++++++++-
fs/namespace.c | 34 ++++++++++++++++++++--------------
fs/proc/root.c | 3 ++-
fs/super.c | 38 +++++++++++++++++++++++++++++++++-----
include/linux/fs.h | 9 +++++++++
include/linux/mount.h | 1 +
include/linux/user_namespace.h | 8 ++++++++
kernel/user_namespace.c | 14 ++++++++++++++
security/commoncap.c | 4 +++-
security/security.c | 10 +++++++++-
security/selinux/hooks.c | 16 +++++++++++++++-
security/smack/smack_lsm.c | 12 ++++++++++--
14 files changed, 134 insertions(+), 28 deletions(-)