user namespace and namespace infrastructure completion

The following series of changes completes the user namespace and adds the much too long delay bits of namespace infrastructure.

This series of changes adds unprivilged creation of all namespaces support for creating a user namespace with unshare, and support for entering a user namespace with setns.

The proc namespace files are converted into magic symlinks to avoid problems with dentry caching excessively keeping a namespace alive and dentry caching allowing the ptrace_may_access checks to be bypassed.

The proc namespace now have inode numbers that are always the same for the same user namespace allowing stat to test if two file descriptors refer to the same namespace.

Eric W. Biederman (16):
userns: Ignore suid and sgid on binaries if the uid or gid can not be mapped
userns: Allow unprivileged users to create user namespaces.
userns: Allow chown and setgid preservation
userns: Allow setting a userns mapping to your current uid.
userns: Allow unprivileged users to create new namespaces
userns: Allow unprivileged use of setns.
userns: Make create_new_namespaces take a user_ns parameter
userns: Kill task_user_ns
userns: Implent proc namespace operations
userns: Implement unshare of the user namespace
procfs: Print task uids and gids in the userns that opened the proc file
userns: For /proc/self/{uid,gid}_map derive the lower userns from the struct file
userns: Allow unprivilged mounts of proc and sysfs
proc: Generalize proc inode allocation
proc: Fix the namespace inode permission checks.
proc: Usable inode numbers for the namespace file descriptors.

 fs/attr.c                      |   11 ++-
 fs/exec.c                      |    9 +--
 fs/mount.h                     |    1 +
 fs/namespace.c                 |   14 +++
 fs/proc/array.c                |    2 +-
 fs/proc/generic.c              |   26 +++---
 fs/proc/inode.c                |    6 +-
 fs/proc/namespaces.c           |  177 +++++++++++++++++++++++++++++++++++-----
 fs/proc/root.c                 |    1 +
 fs/sysfs/mount.c               |    1 +
 include/linux/cred.h           |    2 -
 include/linux/ipc_namespace.h  |    9 ++-
 include/linux/nsproxy.h        |    2 +-
 include/linux/pid_namespace.h  |    1 +
 include/linux/proc_fs.h        |   18 ++++-
 include/linux/user_namespace.h |   10 ++
 include/linux/utsname.h        |    7 +-
 include/net/net_namespace.h    |    2 +
 init/version.c                 |    2 +
 ipc/msgutil.c                  |    2 +
 ipc/namespace.c                |   32 ++++++--
 kernel/fork.c                  |   33 +++++---
 kernel/nsproxy.c               |   34 ++++----
 kernel/pid.c                   |    1 +
 kernel/pid_namespace.c         |   12 +++
 kernel/ptrace.c                |   10 ++-
 kernel/sched/core.c            |   10 ++-
 kernel/user.c                  |    2 +
 kernel/user_namespace.c        |  147 +++++++++++++++++++++++++++++----
 kernel/utsname.c               |   33 ++++++--
 net/core/net_namespace.c       |   31 +++++++-
 security/yama/yama_lsm.c       |   12 ++-
 32 files changed, 535 insertions(+), 125 deletions(-)