Pull request: nsmount updates

[Seth Forshee]

These commits bring xenial up to date wrt my branch for upstream. Most
of the changes here are in response to upstream feedback. At a high
level the changes are:

 - A small improvement to the quota code, then disallow enabling quota
   for mounts from non-init user namespaces. Since quota in non-init
   namespaces isn't a requirement in 16.04 we're better off disabling it
   until we know for sure how it will be handled upstream. However ext4
   might temporarily enable quota during mount if recovering from an
   unclean unmount, so the kernel needs to be able to handle it.

 - Revert the way capabilities are determined for inodes in userns
   mounts back to how it is upstream, i.e. based on both capabilities
   and inode ownership, but allow a privileged user in s_user_ns to
   chown if the id being changed is invalid and the other id is either
   invalid or an id mapped into s_user_ns. This gives the mounter
   control over inodes with unmappable ids while making it safe to have
   s_user_ns != &init_user_ns for proc and kernfs-based mounts.

 - Fix an incompatibility between cgroup namespaces and user namespace
   mounts. Previously this was fixed as a side effect of another patch,
   but that patch is being reverted.

 - Remove a needless mount option initialization in fuse.

 - Fix a resource leak for an error path in sget_userns().

Thanks,
Seth

---

The following changes since commit ccc522f630c479f635b63a328a16f972ad381144:

  UBUNTU: Ubuntu-4.4.0-16.32 (2016-03-24 14:33:15 -0600)

are available in the git repository at:

  git://git.launchpad.net/~sforshee/+git/ubuntu-xenial nsmount

for you to fetch changes up to 1a2f7ac533e43ed88270375017e1203fc61ef500:

  UBUNTU: SAUCE: fs: fix a posible leak of allocated superblock (2016-04-05 15:06:25 -0500)

----------------------------------------------------------------
Pavel Tikhomirov (1):
      UBUNTU: SAUCE: fs: fix a posible leak of allocated superblock

Seth Forshee (8):
      UBUNTU: SAUCE: quota: Require that qids passed to dqget() be valid and map into s_user_ns
      Revert "UBUNTU: SAUCE: quota: Treat superblock owner as privilged"
      Revert "UBUNTU: SAUCE: fs: Ensure the mounter of a filesystem is privileged towards its inodes"
      Revert "UBUNTU: SAUCE: kernfs: Always set super block owner to init_user_ns"
      Revert "UBUNTU: SAUCE: proc: Always set super block owner to init_user_ns"
      UBUNTU: SAUCE: fs: Allow superblock owner to change ownership of inodes with unmappable ids
      UBUNTU: SAUCE: fuse: Don't initialize user_id or group_id in mount options
      UBUNTU: SAUCE: cgroup: Use a new super block when mounting in a cgroup namespace

 fs/attr.c                   | 47 +++++++++++++++++++++++++++++++++++++++--------
 fs/fuse/inode.c             |  2 --
 fs/inode.c                  |  3 ---
 fs/kernfs/inode.c           |  2 ++
 fs/kernfs/mount.c           |  4 +---
 fs/proc/base.c              |  2 ++
 fs/proc/generic.c           |  3 +++
 fs/proc/proc_sysctl.c       |  2 ++
 fs/proc/root.c              |  2 +-
 fs/quota/dquot.c            |  6 ++++++
 fs/quota/quota.c            |  2 +-
 fs/super.c                  |  4 ++++
 include/linux/cgroup-defs.h |  4 ++++
 kernel/capability.c         | 13 ++++---------
 kernel/cgroup.c             | 69 ++++++++++++++++++++++++++++++---------------------------------------
 15 files changed, 99 insertions(+), 66 deletions(-)