======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/0:2/806 is trying to acquire lock:
ffff888012884358 (&mddev->reconfig_mutex){+.+.}-{4:4}, at: mddev_lock_nointr drivers/md/md.h:734 [inline]
ffff888012884358 (&mddev->reconfig_mutex){+.+.}-{4:4}, at: md_start_sync+0x15a/0x1010 drivers/md/md.c:10275

but task is already holding lock:
ffffc900043b7c40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
ffffc900043b7c40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
ffffc900043b7c40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
ffffc900043b7c40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}:
       process_one_work kernel/workqueue.c:3372 [inline]
       process_scheduled_works+0xc03/0x1630 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

-> #2 ((wq_completion)md_misc){+.+.}-{0:0}:
       touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:4111
       __flush_workqueue+0x148/0x1470 kernel/workqueue.c:4153
       md_alloc+0x32/0xf20 drivers/md/md.c:6334
       md_alloc_and_put+0x1a/0x1f0 drivers/md/md.c:6423
       blk_probe_dev block/genhd.c:888 [inline]
       blk_request_module+0x27d/0x2a0 block/genhd.c:-1
       blkdev_get_no_open+0x3f/0xe0 block/bdev.c:870
       blkdev_open+0x1d7/0x600 block/fops.c:665
       do_dentry_open+0x816/0x1380 fs/open.c:996
       vfs_open+0x3b/0x340 fs/open.c:1101
       do_open fs/namei.c:4837 [inline]
       path_openat+0x1443/0x1d60 fs/namei.c:5000
       do_file_open+0x23e/0x4a0 fs/namei.c:5029
       do_sys_openat2+0x115/0x200 fs/open.c:1417
       do_sys_open fs/open.c:1423 [inline]
       __do_sys_openat fs/open.c:1439 [inline]
       __se_sys_openat fs/open.c:1434 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1434
       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 (major_names_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       blk_probe_dev block/genhd.c:885 [inline]
       blk_request_module+0x35/0x2a0 block/genhd.c:901
       blkdev_get_no_open+0x3f/0xe0 block/bdev.c:870
       bdev_file_open_by_dev+0xa0/0x240 block/bdev.c:1091
       md_import_device+0x2e9/0x650 drivers/md/md.c:3847
       md_add_new_disk+0x669/0x1850 drivers/md/md.c:7549
       md_ioctl+0x200a/0x2610 drivers/md/md.c:8499
       blkdev_ioctl+0x5e3/0x740 block/ioctl.c:798
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       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

-> #0 (&mddev->reconfig_mutex){+.+.}-{4:4}:
       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
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       mddev_lock_nointr drivers/md/md.h:734 [inline]
       md_start_sync+0x15a/0x1010 drivers/md/md.c:10275
       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:
  &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/0:2/806: 2, last CPU#0:
 #0: ffff88801fbfe940 ((wq_completion)md_misc){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffff88801fbfe940 ((wq_completion)md_misc){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffff88801fbfe940 ((wq_completion)md_misc){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #0: ffff88801fbfe940 ((wq_completion)md_misc){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #1: ffffc900043b7c40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffc900043b7c40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffc900043b7c40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #1: ffffc900043b7c40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479

stack backtrace:
CPU: 0 UID: 0 PID: 806 Comm: kworker/0:2 Not tainted syzkaller #0 PREEMPT(full) 
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_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
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
 mddev_lock_nointr drivers/md/md.h:734 [inline]
 md_start_sync+0x15a/0x1010 drivers/md/md.c:10275
 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
 </TASK>