====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ udevd/15902 is trying to acquire lock: ffffffff8e2f5140 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:316 [inline] ffffffff8e2f5140 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4636 [inline] ffffffff8e2f5140 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4974 [inline] ffffffff8e2f5140 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_node_noprof+0x68/0x660 mm/slub.c:5068 but task is already holding lock: ffffffff8f97df38 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] ffffffff8f97df38 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x281/0x560 lib/kobject_uevent.c:410 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #9 (uevent_sock_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:561 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:580 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast+0x281/0x560 lib/kobject_uevent.c:410 kobject_uevent_env+0x569/0x9e0 lib/kobject_uevent.c:611 device_add+0x544/0xb80 drivers/base/core.c:3742 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/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 -> #8 (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/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 -> #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_enable+0x12/0x20 kernel/jump_label.c:222 tcp_enable_tx_delay+0x253/0x330 net/ipv4/tcp.c:3607 do_tcp_setsockopt+0x136b/0x1f80 net/ipv4/tcp.c:4159 do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2397 __sys_setsockopt net/socket.c:2422 [inline] __do_sys_setsockopt net/socket.c:2428 [inline] __se_sys_setsockopt net/socket.c:2425 [inline] __x64_sys_setsockopt+0x143/0x1b0 net/socket.c:2425 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 -> #6 (sk_lock-AF_INET){+.+.}-{0:0}: lock_sock_nested+0x41/0x130 net/core/sock.c:3837 lock_sock include/net/sock.h:1713 [inline] inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:913 nbd_mark_nsock_dead+0x2cb/0x550 drivers/block/nbd.c:319 recv_work+0x1d0c/0x1e40 drivers/block/nbd.c:1030 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/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 -> #5 (&nsock->tx_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:561 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:580 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x373/0x1000 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x4af/0x1a00 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+0xd45/0x1590 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xda/0x1a0 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x16f/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/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 -> #4 (&cmd->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:561 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:580 nbd_queue_rq+0xc1/0x1000 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x4af/0x1a00 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+0xd45/0x1590 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xda/0x1a0 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x16f/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/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 -> #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+0x6b8/0xdb0 block/genhd.c:531 add_disk_fwnode+0x100/0x3a0 block/genhd.c:600 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:1362 do_initcall_level+0x10a/0x1a0 init/main.c:1424 do_initcalls+0x59/0xa0 init/main.c:1440 kernel_init_freeable+0x29d/0x3e0 init/main.c:1675 kernel_init+0x22/0x1d0 init/main.c:1565 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/rtmutex_api.c:561 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:580 elevator_change+0x1af/0x480 block/elevator.c:679 elv_iosched_store+0x504/0x630 block/elevator.c:826 queue_attr_store+0x207/0x2b0 block/blk-sysfs.c:906 kernfs_fop_write_iter+0x3a5/0x540 fs/kernfs/file.c:345 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x61e/0xbb0 fs/read_write.c:687 ksys_write+0x156/0x270 fs/read_write.c:739 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)#66){++++}-{0:0}: blk_alloc_queue+0x54c/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 null_add_dev+0xe8a/0x1d70 drivers/block/null_blk/main.c:2017 null_create_dev drivers/block/null_blk/main.c:2114 [inline] null_init+0x1e3/0x390 drivers/block/null_blk/main.c:2178 do_one_initcall+0x250/0x870 init/main.c:1362 do_initcall_level+0x10a/0x1a0 init/main.c:1424 do_initcalls+0x59/0xa0 init/main.c:1440 kernel_init_freeable+0x29d/0x3e0 init/main.c:1675 kernel_init+0x22/0x1d0 init/main.c:1565 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:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 __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] kmem_cache_alloc_node_noprof+0x68/0x660 mm/slub.c:5068 __alloc_skb+0x1db/0x7a0 net/core/skbuff.c:704 alloc_skb include/linux/skbuff.h:1384 [inline] alloc_uevent_skb+0x7d/0x230 lib/kobject_uevent.c:289 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline] kobject_uevent_net_broadcast+0x2fd/0x560 lib/kobject_uevent.c:410 kobject_uevent_env+0x569/0x9e0 lib/kobject_uevent.c:611 nbd_config_put+0x2d4/0x7f0 drivers/block/nbd.c:1481 nbd_release+0x101/0x140 drivers/block/nbd.c:1797 bdev_release+0x57c/0x690 block/bdev.c:-1 blkdev_release+0x15/0x20 block/fops.c:682 __fput+0x42a/0xa80 fs/file_table.c:512 fput_close_sync+0x11f/0x240 fs/file_table.c:617 __do_sys_close fs/open.c:1560 [inline] __se_sys_close fs/open.c:1545 [inline] __x64_sys_close+0x7e/0x110 fs/open.c:1545 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 other info that might help us debug this: Chain exists of: fs_reclaim --> cpuhp_state-up --> uevent_sock_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(uevent_sock_mutex); lock(cpuhp_state-up); lock(uevent_sock_mutex); lock(fs_reclaim); *** DEADLOCK *** locks held by udevd/15902: 3, last CPU#0: #0: ffff888026c6f4c8 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1be/0x690 block/bdev.c:1173 #1: ffff8880267a8a48 (&nbd->config_lock){+.+.}-{4:4}, at: refcount_dec_and_mutex_lock+0x30/0xa0 lib/refcount.c:118 #2: ffffffff8f97df38 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] #2: ffffffff8f97df38 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x281/0x560 lib/kobject_uevent.c:410 stack backtrace: CPU: 0 UID: 0 PID: 15902 Comm: udevd Tainted: G L syzkaller #0 PREEMPT_{RT,(full)} Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219 check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 __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] kmem_cache_alloc_node_noprof+0x68/0x660 mm/slub.c:5068 __alloc_skb+0x1db/0x7a0 net/core/skbuff.c:704 alloc_skb include/linux/skbuff.h:1384 [inline] alloc_uevent_skb+0x7d/0x230 lib/kobject_uevent.c:289 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline] kobject_uevent_net_broadcast+0x2fd/0x560 lib/kobject_uevent.c:410 kobject_uevent_env+0x569/0x9e0 lib/kobject_uevent.c:611 nbd_config_put+0x2d4/0x7f0 drivers/block/nbd.c:1481 nbd_release+0x101/0x140 drivers/block/nbd.c:1797 bdev_release+0x57c/0x690 block/bdev.c:-1 blkdev_release+0x15/0x20 block/fops.c:682 __fput+0x42a/0xa80 fs/file_table.c:512 fput_close_sync+0x11f/0x240 fs/file_table.c:617 __do_sys_close fs/open.c:1560 [inline] __se_sys_close fs/open.c:1545 [inline] __x64_sys_close+0x7e/0x110 fs/open.c:1545 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 RIP: 0033:0x7fb92ccab407 Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff RSP: 002b:00007fffbe343210 EFLAGS: 00000202 ORIG_RAX: 0000000000000003 RAX: ffffffffffffffda RBX: 00007fb92cbbd880 RCX: 00007fb92ccab407 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000008 RBP: 00007fb92cbbd6e8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000002 R13: 000055fbf1004190 R14: 0000000000000008 R15: 000055fbf113e8e0