======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L      
------------------------------------------------------
kworker/2:3/2341 is trying to acquire lock:
ffff88802ec76358 (&mddev->reconfig_mutex){+.+.}-{4:4}, at: mddev_lock_nointr drivers/md/md.h:734 [inline]
ffff88802ec76358 (&mddev->reconfig_mutex){+.+.}-{4:4}, at: md_start_sync+0xc4/0xea0 drivers/md/md.c:10275

but task is already holding lock:
ffffc9000c04fd08 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_one_work+0xa2c/0x1b10 kernel/workqueue.c:3471

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       process_one_work+0xa32/0x1b10 kernel/workqueue.c:3471
       process_scheduled_works kernel/workqueue.c:3578 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
       kthread+0x373/0x450 kernel/kthread.c:436
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 ((wq_completion)md_misc){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       touch_wq_lockdep_map+0xad/0x1c0 kernel/workqueue.c:4272
       __flush_workqueue+0x131/0x1200 kernel/workqueue.c:4314
       md_alloc+0x30/0x10a0 drivers/md/md.c:6334
       md_alloc_and_put drivers/md/md.c:6423 [inline]
       md_probe drivers/md/md.c:6439 [inline]
       md_probe+0x73/0xf0 drivers/md/md.c:6434
       blk_probe_dev+0x149/0x1e0 block/genhd.c:888
       blk_request_module+0x16/0xc0 block/genhd.c:901
       blkdev_get_no_open+0x9b/0xf0 block/bdev.c:870
       blkdev_open+0x141/0x4f0 block/fops.c:677
       do_dentry_open+0x674/0x1470 fs/open.c:1000
       vfs_open_consume+0xcc/0x460 fs/open.c:1131
       do_open fs/namei.c:4845 [inline]
       path_openat+0x1547/0x23f0 fs/namei.c:5010
       do_file_open+0x20e/0x430 fs/namei.c:5039
       do_sys_openat2+0x163/0x1d0 fs/open.c:1442
       do_sys_open fs/open.c:1448 [inline]
       __do_sys_openat fs/open.c:1464 [inline]
       __se_sys_openat fs/open.c:1459 [inline]
       __x64_sys_openat+0x12d/0x210 fs/open.c:1459
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (major_names_lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19f/0x1c10 kernel/locking/mutex.c:821
       blk_probe_dev+0x28/0x1e0 block/genhd.c:885
       blk_request_module+0x16/0xc0 block/genhd.c:901
       blkdev_get_no_open+0x9b/0xf0 block/bdev.c:870
       bdev_file_open_by_dev block/bdev.c:1091 [inline]
       bdev_file_open_by_dev+0x70/0x210 block/bdev.c:1079
       md_import_device+0x120/0x360 drivers/md/md.c:3847
       md_add_new_disk+0xdbf/0x1820 drivers/md/md.c:7656
       md_ioctl+0x2be7/0x36c0 drivers/md/md.c:8499
       blkdev_ioctl+0x5ad/0x6f0 block/ioctl.c:798
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&mddev->reconfig_mutex){+.+.}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19f/0x1c10 kernel/locking/mutex.c:821
       mddev_lock_nointr drivers/md/md.h:734 [inline]
       md_start_sync+0xc4/0xea0 drivers/md/md.c:10275
       process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495
       process_scheduled_works kernel/workqueue.c:3578 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
       kthread+0x373/0x450 kernel/kthread.c:436
       ret_from_fork+0x730/0xd60 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:
  &mddev->reconfig_mutex --> (wq_completion)md_misc --> (work_completion)(&mddev->sync_work)

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock((work_completion)(&mddev->sync_work));
                               lock((wq_completion)md_misc);
                               lock((work_completion)(&mddev->sync_work));
  lock(&mddev->reconfig_mutex);

 *** DEADLOCK ***

locks held by kworker/2:3/2341: 2, last CPU#2:
 #0: ffff88801dfd9148 ((wq_completion)md_misc){+.+.}-{0:0}, at: process_one_work+0x1461/0x1b10 kernel/workqueue.c:3470
 #1: ffffc9000c04fd08 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_one_work+0xa2c/0x1b10 kernel/workqueue.c:3471

stack backtrace:
CPU: 2 UID: 0 PID: 2341 Comm: kworker/2:3 Tainted: G             L       syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: md_misc md_start_sync
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
 lock_acquire kernel/locking/lockdep.c:5942 [inline]
 lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x19f/0x1c10 kernel/locking/mutex.c:821
 mddev_lock_nointr drivers/md/md.h:734 [inline]
 md_start_sync+0xc4/0xea0 drivers/md/md.c:10275
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495
 process_scheduled_works kernel/workqueue.c:3578 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>