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

blk-mq: don't touch ->tagset in blk_mq_get_sq_hctx

blk_mq_run_hw_queues() could be run when there isn't queued request and
after queue is cleaned up, at that time tagset is freed, because tagset
lifetime is covered by driver, and often freed after blk_cleanup_queue()
returns.

So don't touch ->tagset for figuring out current default hctx by the mapping
built in request queue, so use-after-free on tagset can be avoided. Meantime
this way should be fast than retrieving mapping from tagset.

https://git.kernel.org/stable/c/460aa288c5cd0544dcf933a2f0ad0e8c6d2d35ff

https://git.kernel.org/stable/c/5d05426e2d5fd7df8afc866b78c36b37b00188b7

https://git.kernel.org/stable/c/70fdd922c7bf8949f8df109cf2635dff64c90392

https://git.kernel.org/stable/c/b140bac470b4f707cda59c7266214246238661df