namespaces: Simplify copy_namespaces so it is clear what is going on.

Remove the test for the impossible case where tsk->nsproxy == NULL.  Fork
will never be called with tsk->nsproxy == NULL.

Only call get_nsproxy when we don't need to generate a new_nsproxy,
and mark the case where we don't generate a new nsproxy as likely.

Remove the code to drop an unnecessarily acquired nsproxy value.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 11 insertions, 24 deletions

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index d9afd256318f..a1ed01139276 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -125,22 +125,16 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
         struct nsproxy *old_ns = tsk->nsproxy;
         struct user_namespace *user_ns = task_cred_xxx(tsk, user_ns);
         struct nsproxy *new_ns;
-        int err = 0;
 
-        if (!old_ns)
+        if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
+                              CLONE_NEWPID | CLONE_NEWNET)))) {
+                get_nsproxy(old_ns);
                 return 0;
-
-        get_nsproxy(old_ns);
-
-        if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
-                                CLONE_NEWPID | CLONE_NEWNET)))
-                return 0;
-
-        if (!ns_capable(user_ns, CAP_SYS_ADMIN)) {
-                err = -EPERM;
-                goto out;
         }
 
+        if (!ns_capable(user_ns, CAP_SYS_ADMIN))
+                return -EPERM;
+
         /*
          * CLONE_NEWIPC must detach from the undolist: after switching
          * to a new ipc namespace, the semaphore arrays from the old
@@ -149,22 +143,15 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
          * it along with CLONE_NEWIPC.
          */
         if ((flags & (CLONE_NEWIPC | CLONE_SYSVSEM)) ==
-                (CLONE_NEWIPC | CLONE_SYSVSEM)) {
-                err = -EINVAL;
-                goto out;
-        }
+                (CLONE_NEWIPC | CLONE_SYSVSEM)) 
+                return -EINVAL;
 
         new_ns = create_new_namespaces(flags, tsk, user_ns, tsk->fs);
-        if (IS_ERR(new_ns)) {
-                err = PTR_ERR(new_ns);
-                goto out;
-        }
+        if (IS_ERR(new_ns))
+                return  PTR_ERR(new_ns);
 
         tsk->nsproxy = new_ns;
-
-out:
-        put_nsproxy(old_ns);
-        return err;
+        return 0;
 }
 
 void free_nsproxy(struct nsproxy *ns)