syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
kworker/u9:2/1562 is trying to acquire lock:
ffff88801be9d210 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_link_sibling+0x4ed/0x5c0 fs/kernfs/dir.c:411

but task is already holding lock:
ffff88801be9d180 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:826

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #10 (&root->kernfs_rwsem){++++}-{4:4}:
       down_write+0x96/0x200 kernel/locking/rwsem.c:1625
       kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:826
       kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1131
       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+0x250/0x870 init/main.c:1392
       do_initcall_level+0x104/0x190 init/main.c:1454
       do_initcalls+0x59/0xa0 init/main.c:1470
       kernel_init_freeable+0x2a6/0x3e0 init/main.c:1703
       kernel_init+0x1d/0x1d0 init/main.c:1593
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #9 (cpuhp_state_mutex){+.+.}-{4:4}:

-> #8 (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_disable+0x12/0x20 kernel/jump_label.c:247
       __inet_hash_connect+0x25bb/0x25c0 net/ipv4/inet_hashtables.c:1083
       tcp_v4_connect+0xd5f/0x19b0 net/ipv4/tcp_ipv4.c:306
       __inet_stream_connect+0x25a/0xdd0 net/ipv4/af_inet.c:684
       inet_stream_connect+0x66/0xa0 net/ipv4/af_inet.c:755
       __sys_connect_file net/socket.c:2148 [inline]
       __sys_connect+0x312/0x450 net/socket.c:2167
       __do_sys_connect net/socket.c:2173 [inline]
       __se_sys_connect net/socket.c:2170 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2170
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #7 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100 net/core/sock.c:3783
       lock_sock include/net/sock.h:1713 [inline]
       inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:915
       nbd_mark_nsock_dead+0x2e9/0x560 drivers/block/nbd.c:318
       recv_work+0x1c2e/0x1d40 drivers/block/nbd.c:1021
       process_one_work kernel/workqueue.c:3302 [inline]
       process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
       worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #6 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:632 [inline]
       __mutex_lock+0x1a3/0x1550 kernel/locking/mutex.c:806
       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+0x2f4/0xa40 block/blk-core.c:753
       submit_bh fs/buffer.c:2735 [inline]
       block_read_full_folio+0x7b7/0x830 fs/buffer.c:2351
       filemap_read_folio+0x137/0x3b0 mm/filemap.c:2502
       do_read_cache_folio+0x358/0x590 mm/filemap.c:4107
       read_mapping_folio include/linux/pagemap.h:1017 [inline]
       read_part_sector+0xb6/0x2b0 block/partitions/core.c:724
       adfspart_check_ICS+0xb1/0x960 block/partitions/acorn.c:356
       check_partition block/partitions/core.c:143 [inline]
       blk_add_partitions block/partitions/core.c:591 [inline]
       bdev_disk_changed+0x817/0x1770 block/partitions/core.c:695
       blkdev_get_whole+0x380/0x510 block/bdev.c:756
       bdev_open+0x31e/0xd30 block/bdev.c:965
       blkdev_open+0x470/0x610 block/fops.c:697
       do_dentry_open+0x785/0x14e0 fs/open.c:947
       vfs_open+0x3b/0x340 fs/open.c:1079
       do_open fs/namei.c:4699 [inline]
       path_openat+0x2e08/0x3860 fs/namei.c:4858
       do_file_open+0x23e/0x4a0 fs/namei.c:4887
       do_sys_openat2+0x113/0x200 fs/open.c:1364
       do_sys_open fs/open.c:1370 [inline]
       __do_sys_openat fs/open.c:1386 [inline]
       __se_sys_openat fs/open.c:1381 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1381
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x15f/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:632 [inline]
       __mutex_lock+0x1a3/0x1550 kernel/locking/mutex.c:806
       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+0x2f4/0xa40 block/blk-core.c:753
       submit_bh fs/buffer.c:2735 [inline]
       block_read_full_folio+0x7b7/0x830 fs/buffer.c:2351
       filemap_read_folio+0x137/0x3b0 mm/filemap.c:2502
       do_read_cache_folio+0x358/0x590 mm/filemap.c:4107
       read_mapping_folio include/linux/pagemap.h:1017 [inline]
       read_part_sector+0xb6/0x2b0 block/partitions/core.c:724
       adfspart_check_ICS+0xb1/0x960 block/partitions/acorn.c:356
       check_partition block/partitions/core.c:143 [inline]
       blk_add_partitions block/partitions/core.c:591 [inline]
       bdev_disk_changed+0x817/0x1770 block/partitions/core.c:695
       blkdev_get_whole+0x380/0x510 block/bdev.c:756
       bdev_open+0x31e/0xd30 block/bdev.c:965
       blkdev_open+0x470/0x610 block/fops.c:697
       do_dentry_open+0x785/0x14e0 fs/open.c:947
       vfs_open+0x3b/0x340 fs/open.c:1079
       do_open fs/namei.c:4699 [inline]
       path_openat+0x2e08/0x3860 fs/namei.c:4858
       do_file_open+0x23e/0x4a0 fs/namei.c:4887
       do_sys_openat2+0x113/0x200 fs/open.c:1364
       do_sys_open fs/open.c:1370 [inline]
       __do_sys_openat fs/open.c:1386 [inline]
       __se_sys_openat fs/open.c:1381 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1381
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x15f/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/0x300 kernel/rcu/srcutree.c:1481
       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+0x3e9/0x4e0 block/blk-sysfs.c:987
       __add_disk+0x677/0xd50 block/genhd.c:528
       add_disk_fwnode+0xfb/0x480 block/genhd.c:597
       add_disk include/linux/blkdev.h:794 [inline]
       nbd_dev_add+0x72c/0xb50 drivers/block/nbd.c:1984
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
       do_one_initcall+0x250/0x870 init/main.c:1392
       do_initcall_level+0x104/0x190 init/main.c:1454
       do_initcalls+0x59/0xa0 init/main.c:1470
       kernel_init_freeable+0x2a6/0x3e0 init/main.c:1703
       kernel_init+0x1d/0x1d0 init/main.c:1593
       ret_from_fork+0x514/0xb70 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:632 [inline]
       __mutex_lock+0x1a3/0x1550 kernel/locking/mutex.c:806
       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:5131 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5176 [inline]
       blk_mq_update_nr_hw_queues+0x5e7/0x1a60 block/blk-mq.c:5241
       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+0x75c/0x8e0 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
       sock_sendmsg_nosec net/socket.c:787 [inline]
       __sock_sendmsg net/socket.c:802 [inline]
       ____sys_sendmsg+0x972/0x9f0 net/socket.c:2698
       ___sys_sendmsg+0x2a5/0x360 net/socket.c:2752
       __sys_sendmsg net/socket.c:2784 [inline]
       __do_sys_sendmsg net/socket.c:2789 [inline]
       __se_sys_sendmsg net/socket.c:2787 [inline]
       __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2787
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x15f/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:4450 [inline]
       __blk_mq_alloc_disk+0x197/0x390 block/blk-mq.c:4497
       nbd_dev_add+0x499/0xb50 drivers/block/nbd.c:1954
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
       do_one_initcall+0x250/0x870 init/main.c:1392
       do_initcall_level+0x104/0x190 init/main.c:1454
       do_initcalls+0x59/0xa0 init/main.c:1470
       kernel_init_freeable+0x2a6/0x3e0 init/main.c:1703
       kernel_init+0x1d/0x1d0 init/main.c:1593
       ret_from_fork+0x514/0xb70 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:4325 [inline]
       fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4339
       might_alloc include/linux/sched/mm.h:317 [inline]
       slab_pre_alloc_hook mm/slub.c:4520 [inline]
       slab_alloc_node mm/slub.c:4875 [inline]
       kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4905
       __kernfs_iattrs+0xdf/0x320 fs/kernfs/inode.c:36
       kernfs_iattrs fs/kernfs/inode.c:59 [inline]
       __kernfs_setattr fs/kernfs/inode.c:72 [inline]
       kernfs_iop_setattr+0xea/0x3f0 fs/kernfs/inode.c:126
       notify_change+0xc1a/0xf40 fs/attr.c:556
       do_truncate+0x1c2/0x250 fs/open.c:68
       handle_truncate fs/namei.c:4307 [inline]
       do_open fs/namei.c:4703 [inline]
       path_openat+0x2f89/0x3860 fs/namei.c:4858
       do_file_open+0x23e/0x4a0 fs/namei.c:4887
       do_sys_openat2+0x113/0x200 fs/open.c:1364
       do_sys_open fs/open.c:1370 [inline]
       __do_sys_openat fs/open.c:1386 [inline]
       __se_sys_openat fs/open.c:1381 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1381
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x15f/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+0x106/0x350 kernel/locking/lockdep.c:5868
       down_write+0x96/0x200 kernel/locking/rwsem.c:1625
       kernfs_link_sibling+0x4ed/0x5c0 fs/kernfs/dir.c:411
       kernfs_add_one+0x1ca/0x5c0 fs/kernfs/dir.c:845
       kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1131
       sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59
       create_dir lib/kobject.c:73 [inline]
       kobject_add_internal+0x62b/0xd00 lib/kobject.c:240
       kobject_add_varg lib/kobject.c:374 [inline]
       kobject_add+0x163/0x240 lib/kobject.c:426
       device_add+0x408/0xbb0 drivers/base/core.c:3629
       hci_conn_add_sysfs+0xd5/0x210 net/bluetooth/hci_sysfs.c:48
       hci_conn_complete_evt+0x84e/0x1290 net/bluetooth/hci_event.c:3200
       hci_event_func net/bluetooth/hci_event.c:7773 [inline]
       hci_event_packet+0x6ab/0xef0 net/bluetooth/hci_event.c:7824
       hci_rx_work+0x3ee/0x1040 net/bluetooth/hci_core.c:4077
       process_one_work kernel/workqueue.c:3302 [inline]
       process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
       worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 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 ***

4 locks held by kworker/u9:2/1562:
 #0: ffff888025d6d140 ((wq_completion)hci0#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3277 [inline]
 #0: ffff888025d6d140 ((wq_completion)hci0#2){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3385
 #1: ffffc90005f1fc40 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3278 [inline]
 #1: ffffc90005f1fc40 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3385
 #2: ffff88805e7b80b8 (&hdev->lock){+.+.}-{4:4}, at: hci_conn_complete_evt+0xcd/0x1290 net/bluetooth/hci_event.c:3117
 #3: ffff88801be9d180 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:826

stack backtrace:
CPU: 0 UID: 0 PID: 1562 Comm: kworker/u9:2 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Workqueue: hci0 hci_rx_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+0x106/0x350 kernel/locking/lockdep.c:5868
 down_write+0x96/0x200 kernel/locking/rwsem.c:1625
 kernfs_link_sibling+0x4ed/0x5c0 fs/kernfs/dir.c:411
 kernfs_add_one+0x1ca/0x5c0 fs/kernfs/dir.c:845
 kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1131
 sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:73 [inline]
 kobject_add_internal+0x62b/0xd00 lib/kobject.c:240
 kobject_add_varg lib/kobject.c:374 [inline]
 kobject_add+0x163/0x240 lib/kobject.c:426
 device_add+0x408/0xbb0 drivers/base/core.c:3629
 hci_conn_add_sysfs+0xd5/0x210 net/bluetooth/hci_sysfs.c:48
 hci_conn_complete_evt+0x84e/0x1290 net/bluetooth/hci_event.c:3200
 hci_event_func net/bluetooth/hci_event.c:7773 [inline]
 hci_event_packet+0x6ab/0xef0 net/bluetooth/hci_event.c:7824
 hci_rx_work+0x3ee/0x1040 net/bluetooth/hci_core.c:4077
 process_one_work kernel/workqueue.c:3302 [inline]
 process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>