Merge sys_clone()/sys_unshare() nsproxy and namespace handling

sys_clone() and sys_unshare() both makes copies of nsproxy and its associated
namespaces.  But they have different code paths.

This patch merges all the nsproxy and its associated namespace copy/clone
handling (as much as possible).  Posted on container list earlier for
feedback.

- Create a new nsproxy and its associated namespaces and pass it back to
  caller to attach it to right process.

- Changed all copy_*_ns() routines to return a new copy of namespace
  instead of attaching it to task->nsproxy.

- Moved the CAP_SYS_ADMIN checks out of copy_*_ns() routines.

- Removed unnessary !ns checks from copy_*_ns() and added BUG_ON()
  just incase.

- Get rid of all individual unshare_*_ns() routines and make use of
  copy_*_ns() instead.

[akpm@osdl.org: cleanups, warning fix]
[clg@fr.ibm.com: remove dup_namespaces() declaration]
[serue@us.ibm.com: fix CONFIG_IPC_NS=n, clone(CLONE_NEWIPC) retval]
[akpm@linux-foundation.org: fix build with CONFIG_SYSVIPC=n]
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <containers@lists.osdl.org>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 37 deletions

diff --git a/kernel/utsname.c b/kernel/utsname.c
index c859164..160c8c5 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -32,58 +32,25 @@ static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
 }
 
 /*
- * unshare the current process' utsname namespace.
- * called only in sys_unshare()
- */
-int unshare_utsname(unsigned long unshare_flags, struct uts_namespace **new_uts)
-{
-	if (unshare_flags & CLONE_NEWUTS) {
-		if (!capable(CAP_SYS_ADMIN))
-			return -EPERM;
-
-		*new_uts = clone_uts_ns(current->nsproxy->uts_ns);
-		if (!*new_uts)
-			return -ENOMEM;
-	}
-
-	return 0;
-}
-
-/*
  * Copy task tsk's utsname namespace, or clone it if flags
  * specifies CLONE_NEWUTS.  In latter case, changes to the
  * utsname of this process won't be seen by parent, and vice
  * versa.
  */
-int copy_utsname(int flags, struct task_struct *tsk)
+struct uts_namespace *copy_utsname(int flags, struct uts_namespace *old_ns)
 {
-	struct uts_namespace *old_ns = tsk->nsproxy->uts_ns;
 	struct uts_namespace *new_ns;
-	int err = 0;
-
-	if (!old_ns)
-		return 0;
 
+	BUG_ON(!old_ns);
 	get_uts_ns(old_ns);
 
 	if (!(flags & CLONE_NEWUTS))
-		return 0;
-
-	if (!capable(CAP_SYS_ADMIN)) {
-		err = -EPERM;
-		goto out;
-	}
+		return old_ns;
 
 	new_ns = clone_uts_ns(old_ns);
-	if (!new_ns) {
-		err = -ENOMEM;
-		goto out;
-	}
-	tsk->nsproxy->uts_ns = new_ns;
 
-out:
 	put_uts_ns(old_ns);
-	return err;
+	return new_ns;
 }
 
 void free_uts_ns(struct kref *kref)