block: disable the elevator int del_gendisk

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: block: disable the elevator int del_gendisk The elevator is only used for file system requests, which are stopped in del_gendisk. Move disabling the elevator and freeing the scheduler tags to the end of del_gendisk instead of doing that work in disk_release and blk_cleanup_queue to avoid a use after free on q->tag_set from disk_release as the tag_set might not be alive at that point. Move the blk_qos_exit call as well, as it just depends on the elevator exit and would be the only reason to keep the not exactly cheap queue freeze in disk_release.

References

• https://git.kernel.org/stable/c/f28699fafc047ec33299da01e928c3a0073c5cc6
• https://git.kernel.org/stable/c/50e34d78815e474d410f342fbe783b18192ca518