freezer: prevent new tasks from inheriting TIF_FREEZE set

Tasks should go to the refrigerator only if explicitly requested to do that by
the freezer and not as a result of inheriting the TIF_FREEZE flag set from the
parent.  Make it happen.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Acked-by: NNigel Cunningham <nigel@nigel.suspend2.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/fork.c

@@ -942,6 +942,7 @@ static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
 	if (!(clone_flags & CLONE_PTRACE))
 		p->ptrace = 0;
 	p->flags = new_flags;
+	clear_freeze_flag(p);
 }
 
 asmlinkage long sys_set_tid_address(int __user *tidptr)