In the Linux kernel, the following vulnerability has been resolved:
blk-cgroup: fix possible deadlock while configuring policy
Following deadlock can be triggered easily by lockdep:
check/1334 is trying to acquire lock: ff1100011d9d0678 (&q->sysfs_lock){+.+.}-{4:4}, at: blk_unregister_queue+0x53/0x180
but task is already holding lock: ff1100011d9d00e0 (&q->q_usage_counter(queue)#3){++++}-{0:0}, at: del_gendisk+0xba/0x110
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&q->q_usage_counter(queue)#3){++++}-{0:0}: blk_queue_enter+0x40b/0x470 blkg_conf_prep+0x7b/0x3c0 tg_set_limit+0x10a/0x3e0 cgroup_file_write+0xc6/0x420 kernfs_fop_write_iter+0x189/0x280 vfs_write+0x256/0x490 ksys_write+0x83/0x190 __x64_sys_write+0x21/0x30 x64_sys_call+0x4608/0x4630 do_syscall_64+0xdb/0x6b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e
-> #1 (&q->rq_qos_mutex){+.+.}-{4:4}: __mutex_lock+0xd8/0xf50 mutex_lock_nested+0x2b/0x40 wbt_init+0x17e/0x280 wbt_enable_default+0xe9/0x140 blk_register_queue+0x1da/0x2e0 __add_disk+0x38c/0x5d0 add_disk_fwnode+0x89/0x250 device_add_disk+0x18/0x30 virtblk_probe+0x13a3/0x1800 virtio_dev_probe+0x389/0x610 really_probe+0x136/0x620 __driver_probe_device+0xb3/0x230 driver_probe_device+0x2f/0xe0 __driver_attach+0x158/0x250 bus_for_each_dev+0xa9/0x130 driver_attach+0x26/0x40 bus_add_driver+0x178/0x3d0 driver_register+0x7d/0x1c0 __register_virtio_driver+0x2c/0x60 virtio_blk_init+0x6f/0xe0 do_one_initcall+0x94/0x540 kernel_init_freeable+0x56a/0x7b0 kernel_init+0x2b/0x270 ret_from_fork+0x268/0x4c0...