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, 7 insertions, 23 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index fd999cab7b57..be5e56bfb73e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1441,10 +1441,9 @@ dput_out:
  * Allocate a new namespace structure and populate it with contents
  * copied from the namespace of the passed in task structure.
  */
-struct mnt_namespace *dup_mnt_ns(struct task_struct *tsk,
+static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
                 struct fs_struct *fs)
 {
-        struct mnt_namespace *mnt_ns = tsk->nsproxy->mnt_ns;
         struct mnt_namespace *new_ns;
         struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
         struct vfsmount *p, *q;
@@ -1509,36 +1508,21 @@ struct mnt_namespace *dup_mnt_ns(struct task_struct *tsk,
         return new_ns;
 }
 
-int copy_mnt_ns(int flags, struct task_struct *tsk)
+struct mnt_namespace *copy_mnt_ns(int flags, struct mnt_namespace *ns,
+                struct fs_struct *new_fs)
 {
-        struct mnt_namespace *ns = tsk->nsproxy->mnt_ns;
         struct mnt_namespace *new_ns;
-        int err = 0;
-
-        if (!ns)
-                return 0;
 
+        BUG_ON(!ns);
         get_mnt_ns(ns);
 
         if (!(flags & CLONE_NEWNS))
-                return 0;
-
-        if (!capable(CAP_SYS_ADMIN)) {
-                err = -EPERM;
-                goto out;
-        }
-
-        new_ns = dup_mnt_ns(tsk, tsk->fs);
-        if (!new_ns) {
-                err = -ENOMEM;
-                goto out;
-        }
+                return ns;
 
-        tsk->nsproxy->mnt_ns = new_ns;
+        new_ns = dup_mnt_ns(ns, new_fs);
 
-out:
         put_mnt_ns(ns);
-        return err;
+        return new_ns;
 }
 
 asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,