pid namespaces: changes to show virtual ids to user

This is the largest patch in the set. Make all (I hope) the places where
the pid is shown to or get from user operate on the virtual pids.

The idea is:
 - all in-kernel data structures must store either struct pid itself
   or the pid's global nr, obtained with pid_nr() call;
 - when seeking the task from kernel code with the stored id one
   should use find_task_by_pid() call that works with global pids;
 - when showing pid's numerical value to the user the virtual one
   should be used, but however when one shows task's pid outside this
   task's namespace the global one is to be used;
 - when getting the pid from userspace one need to consider this as
   the virtual one and use appropriate task/pid-searching functions.

[akpm@linux-foundation.org: build fix]
[akpm@linux-foundation.org: nuther build fix]
[akpm@linux-foundation.org: yet nuther build fix]
[akpm@linux-foundation.org: remove unneeded casts]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
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>

1 files changed, 4 insertions, 2 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 72a2a16e2214..4ac56fe3c394 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -44,6 +44,7 @@
 #include <linux/vmalloc.h>
 #include <linux/blkdev.h>
 #include <linux/delay.h>
+#include <linux/pid_namespace.h>
 #include <linux/smp.h>
 #include <linux/threads.h>
 #include <linux/timer.h>
@@ -1876,7 +1877,7 @@ asmlinkage void schedule_tail(struct task_struct *prev)
         preempt_enable();
 #endif
         if (current->set_child_tid)
-                put_user(current->pid, current->set_child_tid);
+                put_user(task_pid_vnr(current), current->set_child_tid);
 }
 
 /*
@@ -4167,7 +4168,8 @@ struct task_struct *idle_task(int cpu)
  */
 static struct task_struct *find_process_by_pid(pid_t pid)
 {
-        return pid ? find_task_by_pid(pid) : current;
+        return pid ?
+                find_task_by_pid_ns(pid, current->nsproxy->pid_ns) : current;
 }
 
 /* Actually do priority change: must hold rq lock. */