[PATCH] compat_clock_getres shouldn't return -EFAULT if res == NULL

For clock_getres(clockid_t clock_id, struct timespec *res), the specification
says "If res is NULL, the clock resolution is not returned." So this kind of
call should succeed.  The current implementation returns -EFAULT.

The patch fixes the bug in compat_clock_getres().
Signed-off-by: Gordon Jin <gordon.jin@intel.com>
Signed-off-by: Arun Sharma <arun.sharma@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/compat.c

@@ -531,7 +531,7 @@ long compat_clock_getres(clockid_t which_clock,
 	err = sys_clock_getres(which_clock,
 			       (struct timespec __user *) &ts);
 	set_fs(oldfs);
-	if (!err && put_compat_timespec(&ts, tp))
+	if (!err && tp && put_compat_timespec(&ts, tp))
 		return -EFAULT; 
 	return err;
 }