[PATCH 2/4] userns: let copy_ipcs handle setting ipc_ns->user_ns

["Serge E. Hallyn" <serge@hallyn.com>]

To do that, we have to pass in the task_struct of the task which
will own the ipc_ns, so we can assign its user_ns.

Changelog:
	Feb 23: As per Oleg comment, just pass in tsk.  To get the
	        ipc_ns from the nsproxy we need to include nsproxy.h

Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
---
 include/linux/ipc_namespace.h |    7 ++++---
 ipc/namespace.c               |   13 ++++++++-----
 kernel/nsproxy.c              |    7 +------
 3 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 46d2eb4..c079d09 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -5,6 +5,7 @@
 #include <linux/idr.h>
 #include <linux/rwsem.h>
 #include <linux/notifier.h>
+#include <linux/nsproxy.h>
 
 /*
  * ipc namespace events
@@ -93,7 +94,7 @@ static inline int mq_init_ns(struct ipc_namespace *ns) { return 0; }
 
 #if defined(CONFIG_IPC_NS)
 extern struct ipc_namespace *copy_ipcs(unsigned long flags,
-				       struct ipc_namespace *ns);
+				       struct task_struct *tsk);
 static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
 {
 	if (ns)
@@ -104,12 +105,12 @@ static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
 extern void put_ipc_ns(struct ipc_namespace *ns);
 #else
 static inline struct ipc_namespace *copy_ipcs(unsigned long flags,
-		struct ipc_namespace *ns)
+					      struct task_struct *tsk)
 {
 	if (flags & CLONE_NEWIPC)
 		return ERR_PTR(-EINVAL);
 
-	return ns;
+	return tsk->nsproxy->ipc_ns;
 }
 
 static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
diff --git a/ipc/namespace.c b/ipc/namespace.c
index aa18899..3c3e522 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -15,7 +15,8 @@
 
 #include "util.h"
 
-static struct ipc_namespace *create_ipc_ns(struct ipc_namespace *old_ns)
+static struct ipc_namespace *create_ipc_ns(struct task_struct *tsk,
+					   struct ipc_namespace *old_ns)
 {
 	struct ipc_namespace *ns;
 	int err;
@@ -44,17 +45,19 @@ static struct ipc_namespace *create_ipc_ns(struct ipc_namespace *old_ns)
 	ipcns_notify(IPCNS_CREATED);
 	register_ipcns_notifier(ns);
 
-	ns->user_ns = old_ns->user_ns;
-	get_user_ns(ns->user_ns);
+	ns->user_ns = get_user_ns(task_cred_xxx(tsk, user)->user_ns);
 
 	return ns;
 }
 
-struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
+struct ipc_namespace *copy_ipcs(unsigned long flags,
+				struct task_struct *tsk)
 {
+	struct ipc_namespace *ns = tsk->nsproxy->ipc_ns;
+
 	if (!(flags & CLONE_NEWIPC))
 		return get_ipc_ns(ns);
-	return create_ipc_ns(ns);
+	return create_ipc_ns(tsk, ns);
 }
 
 /*
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index ac8a56e..a05d191 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -75,16 +75,11 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
 		goto out_uts;
 	}
 
-	new_nsp->ipc_ns = copy_ipcs(flags, tsk->nsproxy->ipc_ns);
+	new_nsp->ipc_ns = copy_ipcs(flags, tsk);
 	if (IS_ERR(new_nsp->ipc_ns)) {
 		err = PTR_ERR(new_nsp->ipc_ns);
 		goto out_ipc;
 	}
-	if (new_nsp->ipc_ns != tsk->nsproxy->ipc_ns) {
-		put_user_ns(new_nsp->ipc_ns->user_ns);
-		new_nsp->ipc_ns->user_ns = task_cred_xxx(tsk, user)->user_ns;
-		get_user_ns(new_nsp->ipc_ns->user_ns);
-	}
 
 	new_nsp->pid_ns = copy_pid_ns(flags, task_active_pid_ns(tsk));
 	if (IS_ERR(new_nsp->pid_ns)) {
-- 
1.7.0.4