block, bfq: don't move oom_bfqq

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

block, bfq: don't move oom_bfqq

Our test report a UAF:

[ 2073.019181] ==================================================================
[ 2073.019188] BUG: KASAN: use-after-free in __bfq_put_async_bfqq+0xa0/0x168
[ 2073.019191] Write of size 8 at addr ffff8000ccf64128 by task rmmod/72584
[ 2073.019192]
[ 2073.019196] CPU: 0 PID: 72584 Comm: rmmod Kdump: loaded Not tainted 4.19.90-yk #5
[ 2073.019198] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
[ 2073.019200] Call trace:
[ 2073.019203] dump_backtrace+0x0/0x310
[ 2073.019206] show_stack+0x28/0x38
[ 2073.019210] dump_stack+0xec/0x15c
[ 2073.019216] print_address_description+0x68/0x2d0
[ 2073.019220] kasan_report+0x238/0x2f0
[ 2073.019224] __asan_store8+0x88/0xb0
[ 2073.019229] __bfq_put_async_bfqq+0xa0/0x168
[ 2073.019233] bfq_put_async_queues+0xbc/0x208
[ 2073.019236] bfq_pd_offline+0x178/0x238
[ 2073.019240] blkcg_deactivate_policy+0x1f0/0x420
[ 2073.019244] bfq_exit_queue+0x128/0x178
[ 2073.019249] blk_mq_exit_sched+0x12c/0x160
[ 2073.019252] elevator_exit+0xc8/0xd0
[ 2073.019256] blk_exit_queue+0x50/0x88
[ 2073.019259] blk_cleanup_queue+0x228/0x3d8
[ 2073.019267] null_del_dev+0xfc/0x1e0 [null_blk]
[ 2073.019274] null_exit+0x90/0x114 [null_blk]
[ 2073.019278] __arm64_sys_delete_module+0x358/0x5a0
[ 2073.019282] el0_svc_common+0xc8/0x320
[ 2073.019287] el0_svc_handler+0xf8/0x160
[ 2073.019290] el0_svc+0x10/0x218
[ 2073.019291]
[ 2073.019294] Allocated by task 14163:
[ 2073.019301] kasan_kmalloc+0xe0/0x190
[ 2073.019305] kmem_cache_alloc_node_trace+0x1cc/0x418
[ 2073.019308] bfq_pd_alloc+0x54/0x118
[ 2073.019313] blkcg_activate_policy+0x250/0x460
[ 2073.019317] bfq_create_group_hierarchy+0x38/0x110
[ 2073.019321] bfq_init_queue+0x6d0/0x948
[ 2073.019325] blk_mq_init_sched+0x1d8/0x390
[ 2073.019330] elevator_switch_mq+0x88/0x170
[ 2073.019334] elevator_switch+0x140/0x270
[ 2073.019338] elv_iosched_store+0x1a4/0x2a0
[ 2073.019342] queue_attr_store+0x90/0xe0
[ 2073.019348] sysfs_kf_write+0xa8/0xe8
[ 2073.019351] kernfs_fop_write+0x1f8/0x378
[ 2073.019359] __vfs_write+0xe0/0x360
[ 2073.019363] vfs_write+0xf0/0x270
[ 2073.019367] ksys_write+0xdc/0x1b8
[ 2073.019371] __arm64_sys_write+0x50/0x60
[ 2073.019375] el0_svc_common+0xc8/0x320
[ 2073.019380] el0_svc_handler+0xf8/0x160
[ 2073.019383] el0_svc+0x10/0x218
[ 2073.019385]
[ 2073.019387] Freed by task 72584:
[ 2073.019391] __kasan_slab_free+0x120/0x228
[ 2073.019394] kasan_slab_free+0x10/0x18
[ 2073.019397] kfree+0x94/0x368
[ 2073.019400] bfqg_put+0x64/0xb0
[ 2073.019404] bfqg_and_blkg_put+0x90/0xb0
[ 2073.019408] bfq_put_queue+0x220/0x228
[ 2073.019413] __bfq_put_async_bfqq+0x98/0x168
[ 2073.019416] bfq_put_async_queues+0xbc/0x208
[ 2073.019420] bfq_pd_offline+0x178/0x238
[ 2073.019424] blkcg_deactivate_policy+0x1f0/0x420
[ 2073.019429] bfq_exit_queue+0x128/0x178
[ 2073.019433] blk_mq_exit_sched+0x12c/0x160
[ 2073.019437] elevator_exit+0xc8/0xd0
[ 2073.019440] blk_exit_queue+0x50/0x88
[ 2073.019443] blk_cleanup_queue+0x228/0x3d8
[ 2073.019451] null_del_dev+0xfc/0x1e0 [null_blk]
[ 2073.019459] null_exit+0x90/0x114 [null_blk]
[ 2073.019462] __arm64_sys_delete_module+0x358/0x5a0
[ 2073.019467] el0_svc_common+0xc8/0x320
[ 2073.019471] el0_svc_handler+0xf8/0x160
[ 2073.019474] el0_svc+0x10/0x218
[ 2073.019475]
[ 2073.019479] The buggy address belongs to the object at ffff8000ccf63f00
which belongs to the cache kmalloc-1024 of size 1024
[ 2073.019484] The buggy address is located 552 bytes inside of
1024-byte region [ffff8000ccf63f00, ffff8000ccf64300)
[ 2073.019486] The buggy address belongs to the page:
[ 2073.019492] page:ffff7e000333d800 count:1 mapcount:0 mapping:ffff8000c0003a00 index:0x0 compound_mapcount: 0
[ 2073.020123] flags: 0x7ffff0000008100(slab|head)
[ 2073.020403] raw: 07ffff0000008100 ffff7e0003334c08 ffff7e00001f5a08 ffff8000c0003a00
[ 2073.020409] ra
---truncated---