syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u9:2/5826 is trying to acquire lock:
ffff88801b6d5a20 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_unlink_sibling+0x71/0x180 fs/kernfs/dir.c:424

but task is already holding lock:
ffff88801b6d5988 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_remove_by_name_ns+0x3d/0x130 fs/kernfs/dir.c:1717

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (&root->kernfs_rwsem){++++}-{4:4}:
       down_write+0x96/0x200 kernel/locking/rwsem.c:1590
       kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:796
       kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1098
       internal_create_group+0x425/0x1180 fs/sysfs/group.c:176
       cpuhp_invoke_callback+0x445/0x860 kernel/cpu.c:194
       cpuhp_issue_call+0x430/0x7a0 kernel/cpu.c:-1
       __cpuhp_setup_state_cpuslocked+0x3d9/0x6b0 kernel/cpu.c:2507
       __cpuhp_setup_state+0x3f/0x60 kernel/cpu.c:2536
       do_one_initcall+0x250/0x8d0 init/main.c:1382
       do_initcall_level+0x104/0x190 init/main.c:1444
       do_initcalls+0x59/0xa0 init/main.c:1460
       kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
       kernel_init+0x1d/0x1d0 init/main.c:1582
       ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #8 (cpuhp_state_mutex){+.+.}-{4:4}:

-> #7 (cpu_hotplug_lock){++++}-{0:0}:
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
       cpus_read_lock+0x42/0x160 kernel/cpu.c:490
       static_key_slow_inc+0x12/0x30 kernel/jump_label.c:190
       nbd_reconnect_socket drivers/block/nbd.c:1342 [inline]
       nbd_genl_reconfigure+0x132f/0x1ea0 drivers/block/nbd.c:2431
       genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg net/socket.c:742 [inline]
       ____sys_sendmsg+0x972/0x9f0 net/socket.c:2592
       ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
       __sys_sendmsg net/socket.c:2678 [inline]
       __do_sys_sendmsg net/socket.c:2683 [inline]
       __se_sys_sendmsg net/socket.c:2681 [inline]
       __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776
       nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
       nbd_queue_rq+0x37b/0x1100 drivers/block/nbd.c:1207
       blk_mq_dispatch_rq_list+0xa70/0x1910 block/blk-mq.c:2148
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xdcc/0x1600 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2386
       blk_mq_dispatch_list+0xd16/0xe10 include/linux/spinlock.h:-1
       blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997
       __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
       blk_finish_plug block/blk-core.c:1257 [inline]
       __submit_bio+0x28d/0x580 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753
       submit_bh fs/buffer.c:2826 [inline]
       block_read_full_folio+0x599/0x830 fs/buffer.c:2444
       filemap_read_folio+0x137/0x3b0 mm/filemap.c:2501
       do_read_cache_folio+0x358/0x590 mm/filemap.c:4101
       read_mapping_folio include/linux/pagemap.h:1028 [inline]
       read_part_sector+0xb6/0x2b0 block/partitions/core.c:723
       adfspart_check_ICS+0xa5/0xa40 block/partitions/acorn.c:360
       check_partition block/partitions/core.c:142 [inline]
       blk_add_partitions block/partitions/core.c:590 [inline]
       bdev_disk_changed+0x7ba/0x1550 block/partitions/core.c:694
       blkdev_get_whole+0x380/0x510 block/bdev.c:764
       bdev_open+0x31e/0xd30 block/bdev.c:973
       blkdev_open+0x470/0x610 block/fops.c:697
       do_dentry_open+0x785/0x14e0 fs/open.c:949
       vfs_open+0x3b/0x340 fs/open.c:1081
       do_open fs/namei.c:4671 [inline]
       path_openat+0x2e08/0x3860 fs/namei.c:4830
       do_file_open+0x23e/0x4a0 fs/namei.c:4859
       do_sys_openat2+0x113/0x200 fs/open.c:1366
       do_sys_open fs/open.c:1372 [inline]
       __do_sys_openat fs/open.c:1388 [inline]
       __se_sys_openat fs/open.c:1383 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1383
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #5 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776
       nbd_queue_rq+0xc6/0x1100 drivers/block/nbd.c:1199
       blk_mq_dispatch_rq_list+0xa70/0x1910 block/blk-mq.c:2148
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xdcc/0x1600 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2386
       blk_mq_dispatch_list+0xd16/0xe10 include/linux/spinlock.h:-1
       blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997
       __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
       blk_finish_plug block/blk-core.c:1257 [inline]
       __submit_bio+0x28d/0x580 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753
       submit_bh fs/buffer.c:2826 [inline]
       block_read_full_folio+0x599/0x830 fs/buffer.c:2444
       filemap_read_folio+0x137/0x3b0 mm/filemap.c:2501
       do_read_cache_folio+0x358/0x590 mm/filemap.c:4101
       read_mapping_folio include/linux/pagemap.h:1028 [inline]
       read_part_sector+0xb6/0x2b0 block/partitions/core.c:723
       adfspart_check_ICS+0xa5/0xa40 block/partitions/acorn.c:360
       check_partition block/partitions/core.c:142 [inline]
       blk_add_partitions block/partitions/core.c:590 [inline]
       bdev_disk_changed+0x7ba/0x1550 block/partitions/core.c:694
       blkdev_get_whole+0x380/0x510 block/bdev.c:764
       bdev_open+0x31e/0xd30 block/bdev.c:973
       blkdev_open+0x470/0x610 block/fops.c:697
       do_dentry_open+0x785/0x14e0 fs/open.c:949
       vfs_open+0x3b/0x340 fs/open.c:1081
       do_open fs/namei.c:4671 [inline]
       path_openat+0x2e08/0x3860 fs/namei.c:4830
       do_file_open+0x23e/0x4a0 fs/namei.c:4859
       do_sys_openat2+0x113/0x200 fs/open.c:1366
       do_sys_open fs/open.c:1372 [inline]
       __do_sys_openat fs/open.c:1388 [inline]
       __se_sys_openat fs/open.c:1383 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1383
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (set->srcu){.+.+}-{0:0}:
       srcu_lock_sync include/linux/srcu.h:199 [inline]
       __synchronize_srcu+0xca/0x3e0 kernel/rcu/srcutree.c:1505
       elevator_switch+0x1e8/0x7a0 block/elevator.c:576
       elevator_change+0x2cc/0x450 block/elevator.c:681
       elevator_set_default+0x36c/0x430 block/elevator.c:754
       blk_register_queue+0x366/0x430 block/blk-sysfs.c:946
       __add_disk+0x677/0xd50 block/genhd.c:528
       add_disk_fwnode+0xfb/0x480 block/genhd.c:597
       add_disk include/linux/blkdev.h:785 [inline]
       nbd_dev_add+0x72c/0xb50 drivers/block/nbd.c:1984
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
       do_one_initcall+0x250/0x8d0 init/main.c:1382
       do_initcall_level+0x104/0x190 init/main.c:1444
       do_initcalls+0x59/0xa0 init/main.c:1460
       kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
       kernel_init+0x1d/0x1d0 init/main.c:1582
       ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #3 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776
       elevator_change+0x1b3/0x450 block/elevator.c:679
       elevator_set_none+0xb5/0x140 block/elevator.c:769
       blk_mq_elv_switch_none block/blk-mq.c:5110 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5155 [inline]
       blk_mq_update_nr_hw_queues+0x5e7/0x1a60 block/blk-mq.c:5220
       nbd_start_device+0x17f/0xb10 drivers/block/nbd.c:1489
       nbd_genl_connect+0x165b/0x1cf0 drivers/block/nbd.c:2239
       genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg net/socket.c:742 [inline]
       ____sys_sendmsg+0x972/0x9f0 net/socket.c:2592
       ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
       __sys_sendmsg net/socket.c:2678 [inline]
       __do_sys_sendmsg net/socket.c:2683 [inline]
       __se_sys_sendmsg net/socket.c:2681 [inline]
       __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&q->q_usage_counter(io)#49){++++}-{0:0}:
       blk_alloc_queue+0x546/0x680 block/blk-core.c:461
       blk_mq_alloc_queue block/blk-mq.c:4429 [inline]
       __blk_mq_alloc_disk+0x197/0x390 block/blk-mq.c:4476
       nbd_dev_add+0x499/0xb50 drivers/block/nbd.c:1954
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
       do_one_initcall+0x250/0x8d0 init/main.c:1382
       do_initcall_level+0x104/0x190 init/main.c:1444
       do_initcalls+0x59/0xa0 init/main.c:1460
       kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
       kernel_init+0x1d/0x1d0 init/main.c:1582
       ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (fs_reclaim){+.+.}-{0:0}:
       __fs_reclaim_acquire mm/page_alloc.c:4348 [inline]
       fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4362
       might_alloc include/linux/sched/mm.h:317 [inline]
       slab_pre_alloc_hook mm/slub.c:4489 [inline]
       slab_alloc_node mm/slub.c:4843 [inline]
       kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4873
       __kernfs_iattrs+0xdf/0x340 fs/kernfs/inode.c:36
       kernfs_iattrs fs/kernfs/inode.c:61 [inline]
       __kernfs_setattr fs/kernfs/inode.c:74 [inline]
       kernfs_iop_setattr+0xea/0x3f0 fs/kernfs/inode.c:128
       notify_change+0xc1a/0xf40 fs/attr.c:556
       do_truncate+0x1c2/0x250 fs/open.c:68
       handle_truncate fs/namei.c:4279 [inline]
       do_open fs/namei.c:4675 [inline]
       path_openat+0x2f89/0x3860 fs/namei.c:4830
       do_file_open+0x23e/0x4a0 fs/namei.c:4859
       do_sys_openat2+0x113/0x200 fs/open.c:1366
       do_sys_open fs/open.c:1372 [inline]
       __do_sys_openat fs/open.c:1388 [inline]
       __se_sys_openat fs/open.c:1383 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1383
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&root->kernfs_iattr_rwsem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
       down_write+0x96/0x200 kernel/locking/rwsem.c:1590
       kernfs_unlink_sibling+0x71/0x180 fs/kernfs/dir.c:424
       __kernfs_remove+0x3e7/0x660 fs/kernfs/dir.c:1519
       kernfs_remove_by_name_ns+0xaf/0x130 fs/kernfs/dir.c:1722
       kernfs_remove_by_name include/linux/kernfs.h:633 [inline]
       sysfs_unmerge_group+0xd4/0x140 fs/sysfs/group.c:408
       rpm_sysfs_remove drivers/base/power/sysfs.c:823 [inline]
       dpm_sysfs_remove+0x76/0xd0 drivers/base/power/sysfs.c:832
       device_del+0x250/0x8f0 drivers/base/core.c:3853
       device_unregister+0x21/0xf0 drivers/base/core.c:3919
       hci_conn_cleanup net/bluetooth/hci_conn.c:173 [inline]
       hci_conn_del+0xc36/0x1230 net/bluetooth/hci_conn.c:1240
       hci_abort_conn_sync+0xdd0/0x1190 net/bluetooth/hci_sync.c:5753
       hci_cmd_sync_work+0x213/0x400 net/bluetooth/hci_sync.c:332
       process_one_work kernel/workqueue.c:3276 [inline]
       process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
       worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &root->kernfs_iattr_rwsem --> cpuhp_state_mutex --> &root->kernfs_rwsem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&root->kernfs_rwsem);
                               lock(cpuhp_state_mutex);
                               lock(&root->kernfs_rwsem);
  lock(&root->kernfs_iattr_rwsem);

 *** DEADLOCK ***

5 locks held by kworker/u9:2/5826:
 #0: ffff88802aee7948 ((wq_completion)hci5){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3251 [inline]
 #0: ffff88802aee7948 ((wq_completion)hci5){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3359
 #1: ffffc90003147c40 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3252 [inline]
 #1: ffffc90003147c40 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3359
 #2: ffff88801e764ec0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_cmd_sync_work+0x1d3/0x400 net/bluetooth/hci_sync.c:331
 #3: ffff88801e7640c0 (&hdev->lock){+.+.}-{4:4}, at: hci_abort_conn_sync+0xa6f/0x1190 net/bluetooth/hci_sync.c:5734
 #4: ffff88801b6d5988 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_remove_by_name_ns+0x3d/0x130 fs/kernfs/dir.c:1717

stack backtrace:
CPU: 0 UID: 0 PID: 5826 Comm: kworker/u9:2 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: hci5 hci_cmd_sync_work
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
 down_write+0x96/0x200 kernel/locking/rwsem.c:1590
 kernfs_unlink_sibling+0x71/0x180 fs/kernfs/dir.c:424
 __kernfs_remove+0x3e7/0x660 fs/kernfs/dir.c:1519
 kernfs_remove_by_name_ns+0xaf/0x130 fs/kernfs/dir.c:1722
 kernfs_remove_by_name include/linux/kernfs.h:633 [inline]
 sysfs_unmerge_group+0xd4/0x140 fs/sysfs/group.c:408
 rpm_sysfs_remove drivers/base/power/sysfs.c:823 [inline]
 dpm_sysfs_remove+0x76/0xd0 drivers/base/power/sysfs.c:832
 device_del+0x250/0x8f0 drivers/base/core.c:3853
 device_unregister+0x21/0xf0 drivers/base/core.c:3919
 hci_conn_cleanup net/bluetooth/hci_conn.c:173 [inline]
 hci_conn_del+0xc36/0x1230 net/bluetooth/hci_conn.c:1240
 hci_abort_conn_sync+0xdd0/0x1190 net/bluetooth/hci_sync.c:5753
 hci_cmd_sync_work+0x213/0x400 net/bluetooth/hci_sync.c:332
 process_one_work kernel/workqueue.c:3276 [inline]
 process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>