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CVE-2021-47412

Disclosure Date: May 21, 2024
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Description

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.

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General Information

Vendors

  • Linux

Products

  • Linux

Additional Info

Technical Analysis