kernel/sys.c: fix prototype of prctl_get_tid_address()

tid_addr is not a "pointer to (pointer to int in userspace)"; it is in
fact a "pointer to (pointer to int in userspace) in userspace".  So
sparse rightfully complains about passing a kernel pointer to
put_user().
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/sys.c

@@ -2238,12 +2238,12 @@ static int prctl_set_mm(int opt, unsigned long addr,
 }
 
 #ifdef CONFIG_CHECKPOINT_RESTORE
-static int prctl_get_tid_address(struct task_struct *me, int __user **tid_addr)
+static int prctl_get_tid_address(struct task_struct *me, int __user * __user *tid_addr)
 {
 	return put_user(me->clear_child_tid, tid_addr);
 }
 #else
-static int prctl_get_tid_address(struct task_struct *me, int __user **tid_addr)
+static int prctl_get_tid_address(struct task_struct *me, int __user * __user *tid_addr)
 {
 	return -EINVAL;
 }
@@ -2427,7 +2427,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 		error = prctl_set_mm(arg2, arg3, arg4, arg5);
 		break;
 	case PR_GET_TID_ADDRESS:
-		error = prctl_get_tid_address(me, (int __user **)arg2);
+		error = prctl_get_tid_address(me, (int __user * __user *)arg2);
 		break;
 	case PR_SET_CHILD_SUBREAPER:
 		me->signal->is_child_subreaper = !!arg2;