void vmacache_flush_all(struct mm_struct *mm)
{
	struct task_struct *g, *p;
	count_vm_vmacache_event(VMACACHE_FULL_FLUSHES);
	/*
	 * Single threaded tasks need not iterate the entire
	 * list of process. We can avoid the flushing as well
	 * since the mm's seqnum was increased and don't have
	 * to worry about other threads' seqnum. Current's
	 * flush will occur upon the next lookup.
	 */
	if (atomic_read(&mm->mm_users) == 1)
		return;
	rcu_read_lock();
	for_each_process_thread(g, p) {
		/*
		 * Only flush the vmacache pointers as the
		 * mm seqnum is already set and curr's will
		 * be set upon invalidation when the next
		 * lookup is done.
		 */
		if (mm == p->mm)
			vmacache_flush(p);
	}
	rcu_read_unlock();
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.