userns: add a user namespace owner of ipc ns

Changelog:
	Feb 15: Don't set new ipc->user_ns if we didn't create a new
		ipc_ns.
	Feb 23: Move extern declaration to ipc_namespace.h, and group
		fwd declarations at top.

Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 8 insertions, 2 deletions

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index f095ee268833..8b5ce5d3f3ef 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -32,6 +32,7 @@ struct ipc_namespace init_ipc_ns = {
         .mq_msg_max      = DFLT_MSGMAX,
         .mq_msgsize_max  = DFLT_MSGSIZEMAX,
 #endif
+        .user_ns = &init_user_ns,
 };
 
 atomic_t nr_ipc_ns = ATOMIC_INIT(1);
diff --git a/ipc/namespace.c b/ipc/namespace.c
index a1094ff0befa..aa1889962693 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -11,10 +11,11 @@
 #include <linux/slab.h>
 #include <linux/fs.h>
 #include <linux/mount.h>
+#include <linux/user_namespace.h>
 
 #include "util.h"
 
-static struct ipc_namespace *create_ipc_ns(void)
+static struct ipc_namespace *create_ipc_ns(struct ipc_namespace *old_ns)
 {
         struct ipc_namespace *ns;
         int err;
@@ -43,6 +44,9 @@ static struct ipc_namespace *create_ipc_ns(void)
         ipcns_notify(IPCNS_CREATED);
         register_ipcns_notifier(ns);
 
+        ns->user_ns = old_ns->user_ns;
+        get_user_ns(ns->user_ns);
+
         return ns;
 }
 
@@ -50,7 +54,7 @@ struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
 {
         if (!(flags & CLONE_NEWIPC))
                 return get_ipc_ns(ns);
-        return create_ipc_ns();
+        return create_ipc_ns(ns);
 }
 
 /*
@@ -105,6 +109,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
          * order to have a correct value when recomputing msgmni.
          */
         ipcns_notify(IPCNS_REMOVED);
+        put_user_ns(ns->user_ns);
 }
 
 /*