Use find_task_by_vpid in posix timers

All the functions that need to lookup a task by pid in posix timers obtain
this pid from a user space, and thus this value refers to a task in the same
namespace, as the current task lives in.

So the proper behavior is to call find_task_by_vpid() here.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/posix-cpu-timers.c

@@ -20,7 +20,7 @@ static int check_clock(const clockid_t which_clock)
 		return 0;
 
 	read_lock(&tasklist_lock);
-	p = find_task_by_pid(pid);
+	p = find_task_by_vpid(pid);
 	if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
 		   same_thread_group(p, current) : thread_group_leader(p))) {
 		error = -EINVAL;
@@ -305,7 +305,7 @@ int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 		 */
 		struct task_struct *p;
 		rcu_read_lock();
-		p = find_task_by_pid(pid);
+		p = find_task_by_vpid(pid);
 		if (p) {
 			if (CPUCLOCK_PERTHREAD(which_clock)) {
 				if (same_thread_group(p, current)) {
@@ -354,7 +354,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
 		if (pid == 0) {
 			p = current;
 		} else {
-			p = find_task_by_pid(pid);
+			p = find_task_by_vpid(pid);
 			if (p && !same_thread_group(p, current))
 				p = NULL;
 		}
@@ -362,7 +362,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
 		if (pid == 0) {
 			p = current->group_leader;
 		} else {
-			p = find_task_by_pid(pid);
+			p = find_task_by_vpid(pid);
 			if (p && !thread_group_leader(p))
 				p = NULL;
 		}

kernel/posix-timers.c

@@ -404,7 +404,7 @@ static struct task_struct * good_sigevent(sigevent_t * event)
 	struct task_struct *rtn = current->group_leader;
 
 	if ((event->sigev_notify & SIGEV_THREAD_ID ) &&
-		(!(rtn = find_task_by_pid(event->sigev_notify_thread_id)) ||
+		(!(rtn = find_task_by_vpid(event->sigev_notify_thread_id)) ||
 		 !same_thread_group(rtn, current) ||
 		 (event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_SIGNAL))
 		return NULL;