pid namespaces: move alloc_pid() lower in copy_process()

When we create new namespace we will need to allocate the struct pid, that
will have one extra struct upid in array, comparing to the parent.

Thus we need to know the new namespace (if any) in alloc_pid() to init this
struct upid properly, so move the alloc_pid() call lower in copy_process().

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/fork.c

@@ -1040,16 +1040,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	if (p->binfmt && !try_module_get(p->binfmt->module))
 		goto bad_fork_cleanup_put_domain;
 
-	if (pid != &init_struct_pid) {
-		pid = alloc_pid(task_active_pid_ns(p));
-		if (!pid)
-			goto bad_fork_put_binfmt_module;
-	}
-
 	p->did_exec = 0;
 	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
 	copy_flags(clone_flags, p);
-	p->pid = pid_nr(pid);
 	retval = -EFAULT;
 	if (clone_flags & CLONE_PARENT_SETTID)
 		if (put_user(p->pid, parent_tidptr))
@@ -1133,10 +1126,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	p->blocked_on = NULL; /* not blocked yet */
 #endif
 
-	p->tgid = p->pid;
-	if (clone_flags & CLONE_THREAD)
-		p->tgid = current->tgid;
-
 	if ((retval = security_task_alloc(p)))
 		goto bad_fork_cleanup_policy;
 	if ((retval = audit_alloc(p)))
@@ -1162,6 +1151,18 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	if (retval)
 		goto bad_fork_cleanup_namespaces;
 
+	if (pid != &init_struct_pid) {
+		retval = -ENOMEM;
+		pid = alloc_pid(task_active_pid_ns(p));
+		if (!pid)
+			goto bad_fork_cleanup_namespaces;
+	}
+
+	p->pid = pid_nr(pid);
+	p->tgid = p->pid;
+	if (clone_flags & CLONE_THREAD)
+		p->tgid = current->tgid;
+
 	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
 	/*
 	 * Clear TID on mm_release()?
@@ -1259,7 +1260,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		spin_unlock(&current->sighand->siglock);
 		write_unlock_irq(&tasklist_lock);
 		retval = -ERESTARTNOINTR;
-		goto bad_fork_cleanup_namespaces;
+		goto bad_fork_free_pid;
 	}
 
 	if (clone_flags & CLONE_THREAD) {
@@ -1308,6 +1309,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	cgroup_post_fork(p);
 	return p;
 
+bad_fork_free_pid:
+	if (pid != &init_struct_pid)
+		free_pid(pid);
 bad_fork_cleanup_namespaces:
 	exit_task_namespaces(p);
 bad_fork_cleanup_keys:
@@ -1337,9 +1341,6 @@ bad_fork_cleanup_cgroup:
 	cgroup_exit(p, cgroup_callbacks_done);
 bad_fork_cleanup_delays_binfmt:
 	delayacct_tsk_free(p);
-	if (pid != &init_struct_pid)
-		free_pid(pid);
-bad_fork_put_binfmt_module:
 	if (p->binfmt)
 		module_put(p->binfmt->module);
 bad_fork_cleanup_put_domain: