bfq: fix use-after-free in bfq_dispatch_request

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

bfq: fix use-after-free in bfq_dispatch_request

KASAN reports a use-after-free report when doing normal scsi-mq test

[69832.239032] ==================================================================
[69832.241810] BUG: KASAN: use-after-free in bfq_dispatch_request+0x1045/0x44b0
[69832.243267] Read of size 8 at addr ffff88802622ba88 by task kworker/3:1H/155
[69832.244656]
[69832.245007] CPU: 3 PID: 155 Comm: kworker/3:1H Not tainted 5.10.0-10295-g576c6382529e #8
[69832.246626] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[69832.249069] Workqueue: kblockd blk_mq_run_work_fn
[69832.250022] Call Trace:
[69832.250541] dump_stack+0x9b/0xce
[69832.251232] ? bfq_dispatch_request+0x1045/0x44b0
[69832.252243] print_address_description.constprop.6+0x3e/0x60
[69832.253381] ? __cpuidle_text_end+0x5/0x5
[69832.254211] ? vprintk_func+0x6b/0x120
[69832.254994] ? bfq_dispatch_request+0x1045/0x44b0
[69832.255952] ? bfq_dispatch_request+0x1045/0x44b0
[69832.256914] kasan_report.cold.9+0x22/0x3a
[69832.257753] ? bfq_dispatch_request+0x1045/0x44b0
[69832.258755] check_memory_region+0x1c1/0x1e0
[69832.260248] bfq_dispatch_request+0x1045/0x44b0
[69832.261181] ? bfq_bfqq_expire+0x2440/0x2440
[69832.262032] ? blk_mq_delay_run_hw_queues+0xf9/0x170
[69832.263022] __blk_mq_do_dispatch_sched+0x52f/0x830
[69832.264011] ? blk_mq_sched_request_inserted+0x100/0x100
[69832.265101] __blk_mq_sched_dispatch_requests+0x398/0x4f0
[69832.266206] ? blk_mq_do_dispatch_ctx+0x570/0x570
[69832.267147] ? __switch_to+0x5f4/0xee0
[69832.267898] blk_mq_sched_dispatch_requests+0xdf/0x140
[69832.268946] __blk_mq_run_hw_queue+0xc0/0x270
[69832.269840] blk_mq_run_work_fn+0x51/0x60
[69832.278170] process_one_work+0x6d4/0xfe0
[69832.278984] worker_thread+0x91/0xc80
[69832.279726] ? __kthread_parkme+0xb0/0x110
[69832.280554] ? process_one_work+0xfe0/0xfe0
[69832.281414] kthread+0x32d/0x3f0
[69832.282082] ? kthread_park+0x170/0x170
[69832.282849] ret_from_fork+0x1f/0x30
[69832.283573]
[69832.283886] Allocated by task 7725:
[69832.284599] kasan_save_stack+0x19/0x40
[69832.285385] __kasan_kmalloc.constprop.2+0xc1/0xd0
[69832.286350] kmem_cache_alloc_node+0x13f/0x460
[69832.287237] bfq_get_queue+0x3d4/0x1140
[69832.287993] bfq_get_bfqq_handle_split+0x103/0x510
[69832.289015] bfq_init_rq+0x337/0x2d50
[69832.289749] bfq_insert_requests+0x304/0x4e10
[69832.290634] blk_mq_sched_insert_requests+0x13e/0x390
[69832.291629] blk_mq_flush_plug_list+0x4b4/0x760
[69832.292538] blk_flush_plug_list+0x2c5/0x480
[69832.293392] io_schedule_prepare+0xb2/0xd0
[69832.294209] io_schedule_timeout+0x13/0x80
[69832.295014] wait_for_common_io.constprop.1+0x13c/0x270
[69832.296137] submit_bio_wait+0x103/0x1a0
[69832.296932] blkdev_issue_discard+0xe6/0x160
[69832.297794] blk_ioctl_discard+0x219/0x290
[69832.298614] blkdev_common_ioctl+0x50a/0x1750
[69832.304715] blkdev_ioctl+0x470/0x600
[69832.305474] block_ioctl+0xde/0x120
[69832.306232] vfs_ioctl+0x6c/0xc0
[69832.306877] __se_sys_ioctl+0x90/0xa0
[69832.307629] do_syscall_64+0x2d/0x40
[69832.308362] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[69832.309382]
[69832.309701] Freed by task 155:
[69832.310328] kasan_save_stack+0x19/0x40
[69832.311121] kasan_set_track+0x1c/0x30
[69832.311868] kasan_set_free_info+0x1b/0x30
[69832.312699] __kasan_slab_free+0x111/0x160
[69832.313524] kmem_cache_free+0x94/0x460
[69832.314367] bfq_put_queue+0x582/0x940
[69832.315112] __bfq_bfqd_reset_in_service+0x166/0x1d0
[69832.317275] bfq_bfqq_expire+0xb27/0x2440
[69832.318084] bfq_dispatch_request+0x697/0x44b0
[69832.318991] __blk_mq_do_dispatch_sched+0x52f/0x830
[69832.319984] __blk_mq_sched_dispatch_requests+0x398/0x4f0
[69832.321087] blk_mq_sched_dispatch_requests+0xdf/0x140
[69832.322225] __blk_mq_run_hw_queue+0xc0/0x270
[69832.323114] blk_mq_run_work_fn+0x51/0x6
---truncated---