CVE-2021-47412

In the Linux kernel, the following vulnerability has been resolved:

block: don’t call rq_qos_ops->done_bio if the bio isn’t tracked

rq_qos framework is only applied on request based driver, so:

1. rq_qos_done_bio() needn’t to be called for bio based driver

2. rq_qos_done_bio() needn’t to be called for bio which isn’t tracked,
   such as bios ended from error handling code.

Especially in bio_endio():

1. request queue is referred via bio->bi_bdev->bd_disk->queue, which
   may be gone since request queue refcount may not be held in above two
   cases

2. q->rq_qos may be freed in blk_cleanup_queue() when calling into
   __rq_qos_done_bio()

Fix the potential kernel panic by not calling rq_qos_ops->done_bio if
the bio isn’t tracked. This way is safe because both ioc_rqos_done_bio()
and blkcg_iolatency_done_bio() are nop if the bio isn’t tracked.