====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/u9:3/5620 is trying to acquire lock: ffffffff8ee8f980 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:316 [inline] ffffffff8ee8f980 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4636 [inline] ffffffff8ee8f980 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4974 [inline] ffffffff8ee8f980 (fs_reclaim){+.+.}-{0:0}, at: __do_kmalloc_node mm/slub.c:5413 [inline] ffffffff8ee8f980 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_noprof+0xbc/0x720 mm/slub.c:5439 but task is already holding lock: ffffffff8f8120c0 (dpm_list_mtx){+.+.}-{4:4}, at: device_move+0x3c/0x720 drivers/base/core.c:4682 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #8 (dpm_list_mtx){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 device_pm_add+0x7d/0x350 drivers/base/power/main.c:156 device_add+0x4eb/0xb80 drivers/base/core.c:3724 device_create_groups_vargs drivers/base/core.c:4458 [inline] device_create+0x269/0x300 drivers/base/core.c:4497 msr_device_create+0x33/0x50 arch/x86/kernel/msr.c:254 cpuhp_invoke_callback+0x434/0x810 kernel/cpu.c:194 cpuhp_thread_fun+0x362/0x780 kernel/cpu.c:1109 smpboot_thread_fn+0x565/0xa70 kernel/smpboot.c:160 kthread+0x38b/0x480 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 -> #7 (cpuhp_state-up){+.+.}-{0:0}: cpuhp_lock_acquire kernel/cpu.c:103 [inline] cpuhp_thread_fun+0x127/0x780 kernel/cpu.c:1086 smpboot_thread_fn+0x565/0xa70 kernel/smpboot.c:160 kthread+0x38b/0x480 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 (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_genl_reconnect_sock_cb+0x69a/0xbb0 drivers/block/nbd.c:1377 nbd_genl_foreach_sock+0x265/0x450 drivers/block/nbd.c:2152 nbd_genl_reconfigure+0xbbb/0x1040 drivers/block/nbd.c:2477 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800 __sock_sendmsg net/socket.c:815 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2713 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767 __sys_sendmsg net/socket.c:2799 [inline] __do_sys_sendmsg net/socket.c:2804 [inline] __se_sys_sendmsg net/socket.c:2802 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #5 (&nsock->tx_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x373/0xff0 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117 __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+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560 kthread+0x38b/0x480 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 -> #4 (&cmd->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 nbd_queue_rq+0xc1/0xff0 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117 __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+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560 kthread+0x38b/0x480 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 -> #3 (set->srcu){.+.+}-{0:0}: srcu_lock_sync include/linux/srcu.h:210 [inline] __synchronize_srcu+0xc9/0x2f0 kernel/rcu/srcutree.c:1462 elevator_switch+0x1e8/0x7b0 block/elevator.c:576 elevator_change+0x2fa/0x480 block/elevator.c:681 elevator_set_default+0x375/0x440 block/elevator.c:754 blk_register_queue+0x3f3/0x4e0 block/blk-sysfs.c:992 __add_disk+0x6cb/0xe30 block/genhd.c:524 add_disk_fwnode+0x100/0x3a0 block/genhd.c:593 add_disk include/linux/blkdev.h:798 [inline] nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:2026 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743 do_one_initcall+0x250/0x870 init/main.c:1357 do_initcall_level+0x10a/0x1a0 init/main.c:1419 do_initcalls+0x59/0xa0 init/main.c:1435 kernel_init_freeable+0x29d/0x3e0 init/main.c:1670 kernel_init+0x22/0x1d0 init/main.c:1560 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (&q->elevator_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 elevator_change+0x1af/0x480 block/elevator.c:679 elevator_set_none+0xb5/0x140 block/elevator.c:769 blk_mq_elv_switch_none block/blk-mq.c:5102 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5147 [inline] blk_mq_update_nr_hw_queues+0x5ef/0x19f0 block/blk-mq.c:5212 nbd_start_device+0x189/0xb30 drivers/block/nbd.c:1530 nbd_genl_connect+0x167d/0x1cd0 drivers/block/nbd.c:2310 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800 __sock_sendmsg net/socket.c:815 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2713 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767 __sys_sendmsg net/socket.c:2799 [inline] __do_sys_sendmsg net/socket.c:2804 [inline] __se_sys_sendmsg net/socket.c:2802 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&q->q_usage_counter(io)#49){++++}-{0:0}: blk_alloc_queue+0x544/0x690 block/blk-core.c:504 blk_mq_alloc_queue block/blk-mq.c:4420 [inline] __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4467 nbd_dev_add+0x494/0xb60 drivers/block/nbd.c:1996 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743 do_one_initcall+0x250/0x870 init/main.c:1357 do_initcall_level+0x10a/0x1a0 init/main.c:1419 do_initcalls+0x59/0xa0 init/main.c:1435 kernel_init_freeable+0x29d/0x3e0 init/main.c:1670 kernel_init+0x22/0x1d0 init/main.c:1560 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (fs_reclaim){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x15ff/0x2e50 kernel/locking/lockdep.c:5254 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5908 __fs_reclaim_acquire mm/page_alloc.c:4375 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4389 might_alloc include/linux/sched/mm.h:316 [inline] slab_pre_alloc_hook mm/slub.c:4636 [inline] slab_alloc_node mm/slub.c:4974 [inline] __do_kmalloc_node mm/slub.c:5413 [inline] __kmalloc_noprof+0xbc/0x720 mm/slub.c:5439 _kmalloc_noprof include/linux/slab.h:995 [inline] _kzalloc_noprof include/linux/slab.h:1312 [inline] kobject_get_path+0xc5/0x2f0 lib/kobject.c:161 kobject_move+0x2fa/0x720 lib/kobject.c:556 device_move+0xe0/0x720 drivers/base/core.c:4693 hci_conn_del_sysfs+0xb8/0x1a0 net/bluetooth/hci_sysfs.c:75 hci_conn_cleanup net/bluetooth/hci_conn.c:170 [inline] hci_conn_del+0xc3d/0x1200 net/bluetooth/hci_conn.c:1318 hci_abort_conn_sync+0xdd0/0x1190 net/bluetooth/hci_sync.c:5994 hci_cmd_sync_work+0x20b/0x3f0 net/bluetooth/hci_sync.c:332 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560 kthread+0x38b/0x480 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: fs_reclaim --> cpuhp_state-up --> dpm_list_mtx Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(dpm_list_mtx); lock(cpuhp_state-up); lock(dpm_list_mtx); lock(fs_reclaim); *** DEADLOCK *** locks held by kworker/u9:3/5620: 5, last CPU#0: #0: ffff888033c47140 ((wq_completion)hci1){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #0: ffff888033c47140 ((wq_completion)hci1){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #0: ffff888033c47140 ((wq_completion)hci1){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline] #0: ffff888033c47140 ((wq_completion)hci1){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479 #1: ffffc90003d57c40 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #1: ffffc90003d57c40 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #1: ffffc90003d57c40 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline] #1: ffffc90003d57c40 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479 #2: ffff88805ce5cea0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_cmd_sync_work+0x1cb/0x3f0 net/bluetooth/hci_sync.c:331 #3: ffff88805ce5c0b8 (&hdev->lock){+.+.}-{4:4}, at: hci_abort_conn_sync+0xa6f/0x1190 net/bluetooth/hci_sync.c:5975 #4: ffffffff8f8120c0 (dpm_list_mtx){+.+.}-{4:4}, at: device_move+0x3c/0x720 drivers/base/core.c:4682 stack backtrace: CPU: 0 UID: 0 PID: 5620 Comm: kworker/u9:3 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Workqueue: hci1 hci_cmd_sync_work Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2059 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2191 check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x15ff/0x2e50 kernel/locking/lockdep.c:5254 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5908 __fs_reclaim_acquire mm/page_alloc.c:4375 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4389 might_alloc include/linux/sched/mm.h:316 [inline] slab_pre_alloc_hook mm/slub.c:4636 [inline] slab_alloc_node mm/slub.c:4974 [inline] __do_kmalloc_node mm/slub.c:5413 [inline] __kmalloc_noprof+0xbc/0x720 mm/slub.c:5439 _kmalloc_noprof include/linux/slab.h:995 [inline] _kzalloc_noprof include/linux/slab.h:1312 [inline] kobject_get_path+0xc5/0x2f0 lib/kobject.c:161 kobject_move+0x2fa/0x720 lib/kobject.c:556 device_move+0xe0/0x720 drivers/base/core.c:4693 hci_conn_del_sysfs+0xb8/0x1a0 net/bluetooth/hci_sysfs.c:75 hci_conn_cleanup net/bluetooth/hci_conn.c:170 [inline] hci_conn_del+0xc3d/0x1200 net/bluetooth/hci_conn.c:1318 hci_abort_conn_sync+0xdd0/0x1190 net/bluetooth/hci_sync.c:5994 hci_cmd_sync_work+0x20b/0x3f0 net/bluetooth/hci_sync.c:332 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560 kthread+0x38b/0x480 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