static void blk_set_congested(struct request_list *rl, int sync)
{
#ifdef CONFIG_CGROUP_WRITEBACK
	set_wb_congested(rl->blkg->wb_congested, sync);
#else
	/* see blk_clear_congested() */
	if (rl == &rl->q->root_rl)
		set_wb_congested(rl->q->backing_dev_info->wb.congested, sync);
#endif
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.