Just the lookup flags.  Die, bastard, die...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

If CONFIG_NET_NS, CONFIG_UTS_NS and CONFIG_IPC_NS are disabled,
ns_entries[] becomes empty and things like
ns_entries[ARRAY_SIZE(ns_entries) - 1] will explode.
Reported-by: NRichard Weinberger <richard@nod.at>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The namespace cleanup path leaks a dentry which holds a reference count
on a network namespace.  Keeping that network namespace from being freed
when the last user goes away.  Leaving things like vlan devices in the
leaked network namespace.

If you use ip netns add for much real work this problem becomes apparent
pretty quickly.  It light testing the problem hides because frequently
you simply don't notice the leak.

Use d_set_d_op() so that DCACHE_OP_* flags are set correctly.

This issue exists back to 3.0.
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Reported-by: NJustin Pettit <jpettit@nicira.com>
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NJesse Gross <jesse@nicira.com>
Cc: David Miller <davem@davemloft.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

[folded fix for missing magic.h from Tetsuo Handa]
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Don't call iput with the inode half setup to be a namespace filedescriptor.
Instead rearrange the code so that we don't initialize ei->ns_ops until
after I ns_ops->get succeeds, preventing us from invoking ns_ops->put
when ns_ops->get failed.
Reported-by: NIngo Saitz <Ingo.Saitz@stud.uni-hannover.de>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

Spotted-by: NNathan Lynch <ntl@pobox.com>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

Acked-by: NDaniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

Acked-by: NDaniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

Implementing file descriptors for the network namespace
is simple and straight forward.
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NDaniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

Create files under /proc/<pid>/ns/ to allow controlling the
namespaces of a process.

This addresses three specific problems that can make namespaces hard to
work with.
- Namespaces require a dedicated process to pin them in memory.
- It is not possible to use a namespace unless you are the child
  of the original creator.
- Namespaces don't have names that userspace can use to talk about
  them.

The namespace files under /proc/<pid>/ns/ can be opened and the
file descriptor can be used to talk about a specific namespace, and
to keep the specified namespace alive.

A namespace can be kept alive by either holding the file descriptor
open or bind mounting the file someplace else.  aka:
mount --bind /proc/self/ns/net /some/filesystem/path
mount --bind /proc/self/fd/<N> /some/filesystem/path

This allows namespaces to be named with userspace policy.

It requires additional support to make use of these filedescriptors
and that will be comming in the following patches.
Acked-by: NDaniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>