syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.2.3082/14867 is trying to acquire lock:
ffffffff8e8837a0 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline]
ffffffff8e8837a0 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4489 [inline]
ffffffff8e8837a0 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4843 [inline]
ffffffff8e8837a0 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x40/0x660 mm/slub.c:5375

but task is already holding lock:
ffffffff8f17d8a8 (gdp_mutex){+.+.}-{4:4}, at: get_device_parent+0x16f/0x3a0 drivers/base/core.c:3267

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (gdp_mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776
       get_device_parent+0x16f/0x3a0 drivers/base/core.c:3267
       device_add+0x2e1/0xb70 drivers/base/core.c:3614
       device_create_groups_vargs drivers/base/core.c:4372 [inline]
       device_create+0x269/0x300 drivers/base/core.c:4411
       msr_device_create+0x33/0x50 arch/x86/kernel/msr.c:251
       cpuhp_invoke_callback+0x445/0x860 kernel/cpu.c:194
       cpuhp_thread_fun+0x36b/0x780 kernel/cpu.c:1109
       smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
       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

-> #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+0x541/0xa50 kernel/smpboot.c:160
       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

-> #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_disable+0x12/0x20 kernel/jump_label.c:247
       __inet_hash_connect+0x2430/0x2440 net/ipv4/inet_hashtables.c:1074
       tcp_v4_connect+0xd5f/0x19b0 net/ipv4/tcp_ipv4.c:307
       __inet_stream_connect+0x25a/0xdd0 net/ipv4/af_inet.c:685
       inet_stream_connect+0x66/0xa0 net/ipv4/af_inet.c:756
       __sys_connect_file net/socket.c:2154 [inline]
       __sys_connect+0x312/0x450 net/socket.c:2173
       __do_sys_connect net/socket.c:2179 [inline]
       __se_sys_connect net/socket.c:2176 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2176
       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 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_sock_nested+0x48/0x100 net/core/sock.c:3780
       lock_sock include/net/sock.h:1709 [inline]
       inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:919
       nbd_mark_nsock_dead+0x2e9/0x560 drivers/block/nbd.c:318
       sock_shutdown+0x15e/0x260 drivers/block/nbd.c:411
       nbd_clear_sock+0x24/0x170 drivers/block/nbd.c:1427
       nbd_config_put+0x2dd/0x580 drivers/block/nbd.c:1451
       nbd_release+0xfe/0x140 drivers/block/nbd.c:1756
       bdev_release+0x536/0x650 block/bdev.c:-1
       blkdev_release+0x15/0x20 block/fops.c:705
       __fput+0x44f/0xa70 fs/file_table.c:469
       task_work_run+0x1d9/0x270 kernel/task_work.c:233
       resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
       __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
       exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98
       __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
       syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
       syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
       do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #5 (&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:4106
       read_mapping_folio include/linux/pagemap.h:1017 [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: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: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 (&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:4106
       read_mapping_folio include/linux/pagemap.h:1017 [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: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: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

-> #3 (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+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

-> #2 (&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:5112 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5157 [inline]
       blk_mq_update_nr_hw_queues+0x5e7/0x1a60 block/blk-mq.c:5222
       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:792 [inline]
       __sock_sendmsg net/socket.c:807 [inline]
       ____sys_sendmsg+0x972/0x9f0 net/socket.c:2657
       ___sys_sendmsg+0x2a5/0x360 net/socket.c:2711
       __sys_sendmsg net/socket.c:2743 [inline]
       __do_sys_sendmsg net/socket.c:2748 [inline]
       __se_sys_sendmsg net/socket.c:2746 [inline]
       __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2746
       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

-> #1 (&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:4431 [inline]
       __blk_mq_alloc_disk+0x197/0x390 block/blk-mq.c:4478
       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

-> #0 (fs_reclaim){+.+.}-{0:0}:
       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
       __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]
       __kmalloc_cache_noprof+0x40/0x660 mm/slub.c:5375
       kmalloc_noprof include/linux/slab.h:950 [inline]
       kzalloc_noprof include/linux/slab.h:1188 [inline]
       class_dir_create_and_add drivers/base/core.c:3224 [inline]
       get_device_parent+0x255/0x3a0 drivers/base/core.c:3284
       device_add+0x2e1/0xb70 drivers/base/core.c:3614
       wakeup_source_device_create drivers/base/power/wakeup_stats.c:163 [inline]
       wakeup_source_sysfs_add+0x1d3/0x2c0 drivers/base/power/wakeup_stats.c:183
       wakeup_source_register+0x18a/0x380 drivers/base/power/wakeup.c:218
       ep_create_wakeup_source fs/eventpoll.c:1499 [inline]
       ep_insert+0xf34/0x1a40 fs/eventpoll.c:1634
       do_epoll_ctl+0x7f4/0xe80 fs/eventpoll.c:2345
       __do_sys_epoll_ctl fs/eventpoll.c:2396 [inline]
       __se_sys_epoll_ctl fs/eventpoll.c:2387 [inline]
       __x64_sys_epoll_ctl+0x165/0x1b0 fs/eventpoll.c:2387
       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

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> cpuhp_state-up --> gdp_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(gdp_mutex);
                               lock(cpuhp_state-up);
                               lock(gdp_mutex);
  lock(fs_reclaim);

 *** DEADLOCK ***

3 locks held by syz.2.3082/14867:
 #0: ffffffff8e8ef448 (epnested_mutex){+.+.}-{4:4}, at: epoll_mutex_lock+0x4d/0x60 fs/eventpoll.c:2232
 #1: ffff888028915468 (&ep->mtx){+.+.}-{4:4}, at: epoll_mutex_lock+0x4d/0x60 fs/eventpoll.c:2232
 #2: ffffffff8f17d8a8 (gdp_mutex){+.+.}-{4:4}, at: get_device_parent+0x16f/0x3a0 drivers/base/core.c:3267

stack backtrace:
CPU: 0 UID: 0 PID: 14867 Comm: syz.2.3082 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
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
 __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]
 __kmalloc_cache_noprof+0x40/0x660 mm/slub.c:5375
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 class_dir_create_and_add drivers/base/core.c:3224 [inline]
 get_device_parent+0x255/0x3a0 drivers/base/core.c:3284
 device_add+0x2e1/0xb70 drivers/base/core.c:3614
 wakeup_source_device_create drivers/base/power/wakeup_stats.c:163 [inline]
 wakeup_source_sysfs_add+0x1d3/0x2c0 drivers/base/power/wakeup_stats.c:183
 wakeup_source_register+0x18a/0x380 drivers/base/power/wakeup.c:218
 ep_create_wakeup_source fs/eventpoll.c:1499 [inline]
 ep_insert+0xf34/0x1a40 fs/eventpoll.c:1634
 do_epoll_ctl+0x7f4/0xe80 fs/eventpoll.c:2345
 __do_sys_epoll_ctl fs/eventpoll.c:2396 [inline]
 __se_sys_epoll_ctl fs/eventpoll.c:2387 [inline]
 __x64_sys_epoll_ctl+0x165/0x1b0 fs/eventpoll.c:2387
 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
RIP: 0033:0x7f8abbd9c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8abcca3028 EFLAGS: 00000246 ORIG_RAX: 00000000000000e9
RAX: ffffffffffffffda RBX: 00007f8abc015fa0 RCX: 00007f8abbd9c819
RDX: 0000000000000003 RSI: 0000000000000001 RDI: 0000000000000004
RBP: 00007f8abbe32c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000200000000040 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8abc016038 R14: 00007f8abc015fa0 R15: 00007ffc703610f8
 </TASK>