======================================================
WARNING: possible circular locking dependency detected
4.19.89-syzkaller #0 Not tainted
block nbd4: shutting down sockets
------------------------------------------------------
kworker/u5:1/9206 is trying to acquire lock:
0000000028c9d56b (&nbd->config_lock){+.+.}, at: refcount_dec_and_mutex_lock lib/refcount.c:311 [inline]
0000000028c9d56b (&nbd->config_lock){+.+.}, at: refcount_dec_and_mutex_lock+0x52/0x80 lib/refcount.c:306

but task is already holding lock:
000000005bbc889d ((work_completion)(&args->work)){+.+.}, at: process_one_work+0x8b4/0x1750 kernel/workqueue.c:2128

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 ((work_completion)(&args->work)){+.+.}:
       process_one_work+0x90f/0x1750 kernel/workqueue.c:2129
       worker_thread+0x98/0xe40 kernel/workqueue.c:2296
       kthread+0x354/0x420 kernel/kthread.c:246
       ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

-> #1 ((wq_completion)"knbd%d-recv"nbd->index){+.+.}:
       flush_workqueue+0x126/0x14b0 kernel/workqueue.c:2655
       drain_workqueue+0x1b4/0x470 kernel/workqueue.c:2820
       destroy_workqueue+0x21/0x6b0 kernel/workqueue.c:4158
       nbd_config_put+0x3cf/0x860 drivers/block/nbd.c:1161
       nbd_release+0xf6/0x140 drivers/block/nbd.c:1436
       __blkdev_put+0x4d1/0x810 fs/block_dev.c:1804
       blkdev_put+0x98/0x560 fs/block_dev.c:1866
       blkdev_close+0x8b/0xb0 fs/block_dev.c:1873
       __fput+0x2dd/0x8b0 fs/file_table.c:278
       ____fput+0x16/0x20 fs/file_table.c:309
       task_work_run+0x145/0x1c0 kernel/task_work.c:113
       tracehook_notify_resume include/linux/tracehook.h:193 [inline]
       exit_to_usermode_loop+0x273/0x2c0 arch/x86/entry/common.c:167
       prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
       syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
       do_syscall_64+0x53d/0x620 arch/x86/entry/common.c:296
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&nbd->config_lock){+.+.}:
       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903
       __mutex_lock_common kernel/locking/mutex.c:925 [inline]
       __mutex_lock+0xf7/0x1300 kernel/locking/mutex.c:1072
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
       refcount_dec_and_mutex_lock lib/refcount.c:311 [inline]
       refcount_dec_and_mutex_lock+0x52/0x80 lib/refcount.c:306
       nbd_config_put+0x31/0x860 drivers/block/nbd.c:1139
       recv_work+0x19b/0x200 drivers/block/nbd.c:745
       process_one_work+0x989/0x1750 kernel/workqueue.c:2153
       worker_thread+0x98/0xe40 kernel/workqueue.c:2296
       kthread+0x354/0x420 kernel/kthread.c:246
       ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

other info that might help us debug this:

Chain exists of:
  &nbd->config_lock --> (wq_completion)"knbd%d-recv"nbd->index --> (work_completion)(&args->work)

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock((work_completion)(&args->work));
                               lock((wq_completion)"knbd%d-recv"nbd->index);
                               lock((work_completion)(&args->work));
  lock(&nbd->config_lock);

 *** DEADLOCK ***

2 locks held by kworker/u5:1/9206:
 #0: 00000000db18ce1a ((wq_completion)"knbd%d-recv"nbd->index){+.+.}, at: __write_once_size include/linux/compiler.h:220 [inline]
 #0: 00000000db18ce1a ((wq_completion)"knbd%d-recv"nbd->index){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: 00000000db18ce1a ((wq_completion)"knbd%d-recv"nbd->index){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
 #0: 00000000db18ce1a ((wq_completion)"knbd%d-recv"nbd->index){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:59 [inline]
 #0: 00000000db18ce1a ((wq_completion)"knbd%d-recv"nbd->index){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline]
 #0: 00000000db18ce1a ((wq_completion)"knbd%d-recv"nbd->index){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0: 00000000db18ce1a ((wq_completion)"knbd%d-recv"nbd->index){+.+.}, at: process_one_work+0x87e/0x1750 kernel/workqueue.c:2124
 #1: 000000005bbc889d ((work_completion)(&args->work)){+.+.}, at: process_one_work+0x8b4/0x1750 kernel/workqueue.c:2128

stack backtrace:
CPU: 0 PID: 9206 Comm: kworker/u5:1 Not tainted 4.19.89-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: knbd3-recv recv_work
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x197/0x210 lib/dump_stack.c:118
 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1221
 check_prev_add kernel/locking/lockdep.c:1861 [inline]
 check_prevs_add kernel/locking/lockdep.c:1974 [inline]
 validate_chain kernel/locking/lockdep.c:2415 [inline]
 __lock_acquire+0x2e19/0x49c0 kernel/locking/lockdep.c:3411
 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903
 __mutex_lock_common kernel/locking/mutex.c:925 [inline]
 __mutex_lock+0xf7/0x1300 kernel/locking/mutex.c:1072
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
 refcount_dec_and_mutex_lock lib/refcount.c:311 [inline]
 refcount_dec_and_mutex_lock+0x52/0x80 lib/refcount.c:306
 nbd_config_put+0x31/0x860 drivers/block/nbd.c:1139
 recv_work+0x19b/0x200 drivers/block/nbd.c:745
 process_one_work+0x989/0x1750 kernel/workqueue.c:2153
 worker_thread+0x98/0xe40 kernel/workqueue.c:2296
 kthread+0x354/0x420 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
block nbd3: shutting down sockets
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'iosched' (00000000fe7f6f02): kobject_uevent_env
kobject: 'iosched' (00000000fe7f6f02): kobject_uevent_env: filter function caused the event to drop!
kobject: 'loop3' (000000000c9b6397): kobject_uevent_env
kobject: 'iosched' (00000000fe7f6f02): kobject_cleanup, parent           (null)
kobject: 'iosched' (00000000fe7f6f02): calling ktype release
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'iosched': free name
kobject: '1' (0000000070e543fd): kobject_cleanup, parent           (null)
kobject: 'loop3' (000000000c9b6397): fill_kobj_path: path = '/devices/virtual/block/loop3'
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: '1' (0000000070e543fd): calling ktype release
EXT4-fs (sda1): re-mounted. Opts: debug_want_extra_isize=0x0000000000000000,
kobject: 'loop4' (00000000c7390d5d): kobject_uevent_env
kobject: 'loop4' (00000000c7390d5d): fill_kobj_path: path = '/devices/virtual/block/loop4'
kobject: '1': free name
kobject: '0' (000000005b849ca1): kobject_add_internal: parent: 'mq', set: '<NULL>'
kobject: 'loop1' (00000000fda1e6bf): kobject_uevent_env
kobject: 'kvm' (000000001013a681): kobject_uevent_env
kobject: 'cpu0' (0000000050ed4c8f): kobject_add_internal: parent: '0', set: '<NULL>'
kobject: 'kvm' (000000001013a681): fill_kobj_path: path = '/devices/virtual/misc/kvm'
kobject: 'loop1' (00000000fda1e6bf): fill_kobj_path: path = '/devices/virtual/block/loop1'
kobject: 'kvm' (000000001013a681): kobject_uevent_env
kobject: 'loop0' (00000000eeb454c3): kobject_uevent_env
kobject: '0' (000000005b849ca1): kobject_add_internal: parent: 'mq', set: '<NULL>'
kobject: 'kvm' (000000001013a681): fill_kobj_path: path = '/devices/virtual/misc/kvm'
kobject: 'cpu0' (0000000050ed4c8f): kobject_add_internal: parent: '0', set: '<NULL>'
kobject: 'loop0' (00000000eeb454c3): fill_kobj_path: path = '/devices/virtual/block/loop0'
kobject: 'loop1' (00000000fda1e6bf): kobject_uevent_env
kobject: 'cpu1' (0000000057002728): kobject_add_internal: parent: '0', set: '<NULL>'
kobject: 'loop1' (00000000fda1e6bf): fill_kobj_path: path = '/devices/virtual/block/loop1'
kobject: 'iosched' (0000000004a04049): kobject_add_internal: parent: 'queue', set: '<NULL>'
kobject: 'kvm' (000000001013a681): kobject_uevent_env
kobject: 'loop1' (00000000fda1e6bf): kobject_uevent_env
kobject: 'loop1' (00000000fda1e6bf): fill_kobj_path: path = '/devices/virtual/block/loop1'
kobject: 'kvm' (000000001013a681): fill_kobj_path: path = '/devices/virtual/misc/kvm'
kobject: 'iosched' (0000000004a04049): kobject_uevent_env
kobject: 'kvm' (000000001013a681): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'iosched' (0000000004a04049): kobject_uevent_env: filter function caused the event to drop!
kobject: 'kvm' (000000001013a681): fill_kobj_path: path = '/devices/virtual/misc/kvm'
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
block nbd5: Receive control failed (result -107)
kobject: 'nbd5' (000000003cf2fdfa): kobject_uevent_env
kobject: 'nbd5' (000000003cf2fdfa): fill_kobj_path: path = '/devices/virtual/block/nbd5'
block nbd5: shutting down sockets
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'loop0' (00000000eeb454c3): kobject_uevent_env
EXT4-fs (sda1): re-mounted. Opts: debug_want_extra_isize=0x0000000000000000,
kobject: 'loop0' (00000000eeb454c3): fill_kobj_path: path = '/devices/virtual/block/loop0'
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop5' (00000000b0875a6c): kobject_uevent_env
kobject: 'loop5' (00000000b0875a6c): fill_kobj_path: path = '/devices/virtual/block/loop5'
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'loop1' (00000000fda1e6bf): kobject_uevent_env
kobject: 'loop1' (00000000fda1e6bf): fill_kobj_path: path = '/devices/virtual/block/loop1'
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'loop1' (00000000fda1e6bf): kobject_uevent_env
kobject: 'loop1' (00000000fda1e6bf): fill_kobj_path: path = '/devices/virtual/block/loop1'
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'loop0' (00000000eeb454c3): kobject_uevent_env
kobject: 'loop0' (00000000eeb454c3): fill_kobj_path: path = '/devices/virtual/block/loop0'
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'
kobject: 'loop2' (00000000253530c2): kobject_uevent_env
kobject: 'loop2' (00000000253530c2): fill_kobj_path: path = '/devices/virtual/block/loop2'