possible deadlock in get

======================================================
WARNING: possible circular locking dependency detected
6.1.129-syzkaller #0 Not tainted
------------------------------------------------------
syz.8.295/6273 is trying to acquire lock:
ffff0000d502c0e0 (&type->s_umount_key#75){++++}-{3:3}, at: get_super+0x100/0x1f0 fs/super.c:828

but task is already holding lock:
ffff0000ce783998 (&nbd->config_lock){+.+.}-{3:3}, at: nbd_ioctl+0x128/0xc40 drivers/block/nbd.c:1535

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&nbd->config_lock){+.+.}-{3:3}:
       __mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
       refcount_dec_and_mutex_lock+0x40/0x158 lib/refcount.c:118
       nbd_config_put+0x3c/0x6c8 drivers/block/nbd.c:1320
       nbd_release+0xf8/0x130 drivers/block/nbd.c:1624
       blkdev_put+0x4e8/0x6e0
       blkdev_close+0x58/0x94 block/fops.c:514
       __fput+0x1c8/0x7c8 fs/file_table.c:320
       ____fput+0x20/0x30 fs/file_table.c:348
       task_work_run+0x240/0x2f0 kernel/task_work.c:203
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       do_notify_resume+0x2080/0x2cb8 arch/arm64/kernel/signal.c:1132
       prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
       exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
       el0_svc+0x9c/0x168 arch/arm64/kernel/entry-common.c:638
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #1 (&disk->open_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
       blkdev_put+0xec/0x6e0 block/bdev.c:913
       release_journal_dev fs/reiserfs/journal.c:2594 [inline]
       free_journal_ram+0x308/0x374 fs/reiserfs/journal.c:1896
       do_journal_release+0x2f8/0x454 fs/reiserfs/journal.c:1960
       journal_release+0x2c/0x40 fs/reiserfs/journal.c:1971
       reiserfs_put_super+0x204/0x444 fs/reiserfs/super.c:616
       generic_shutdown_super+0x130/0x328 fs/super.c:501
       kill_block_super+0x70/0xdc fs/super.c:1470
       reiserfs_kill_sb+0x134/0x14c fs/reiserfs/super.c:570
       deactivate_locked_super+0xac/0x124 fs/super.c:332
       deactivate_super+0xf0/0x110 fs/super.c:363
       cleanup_mnt+0x394/0x41c fs/namespace.c:1186
       __cleanup_mnt+0x20/0x30 fs/namespace.c:1193
       task_work_run+0x240/0x2f0 kernel/task_work.c:203
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       do_notify_resume+0x2080/0x2cb8 arch/arm64/kernel/signal.c:1132
       prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
       exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
       el0_svc+0x9c/0x168 arch/arm64/kernel/entry-common.c:638
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #0 (&type->s_umount_key#75){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3090 [inline]
       check_prevs_add kernel/locking/lockdep.c:3209 [inline]
       validate_chain kernel/locking/lockdep.c:3825 [inline]
       __lock_acquire+0x3338/0x7680 kernel/locking/lockdep.c:5049
       lock_acquire+0x26c/0x7cc kernel/locking/lockdep.c:5662
       down_read+0x64/0x308 kernel/locking/rwsem.c:1520
       get_super+0x100/0x1f0 fs/super.c:828
       __invalidate_device+0x28/0x108 block/bdev.c:1005
       nbd_clear_sock_ioctl drivers/block/nbd.c:1455 [inline]
       __nbd_ioctl drivers/block/nbd.c:1482 [inline]
       nbd_ioctl+0x2e8/0xc40 drivers/block/nbd.c:1542
       blkdev_ioctl+0x408/0xb40 block/ioctl.c:620
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl fs/ioctl.c:856 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

other info that might help us debug this:

Chain exists of:
  &type->s_umount_key#75 --> &disk->open_mutex --> &nbd->config_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&nbd->config_lock);
                               lock(&disk->open_mutex);
                               lock(&nbd->config_lock);
  lock(&type->s_umount_key#75);

 *** DEADLOCK ***

1 lock held by syz.8.295/6273:
 #0: ffff0000ce783998 (&nbd->config_lock){+.+.}-{3:3}, at: nbd_ioctl+0x128/0xc40 drivers/block/nbd.c:1535

stack backtrace:
CPU: 1 PID: 6273 Comm: syz.8.295 Not tainted 6.1.129-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
 dump_stack+0x1c/0x58 lib/dump_stack.c:113
 print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2048
 check_noncircular+0x2cc/0x378 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3090 [inline]
 check_prevs_add kernel/locking/lockdep.c:3209 [inline]
 validate_chain kernel/locking/lockdep.c:3825 [inline]
 __lock_acquire+0x3338/0x7680 kernel/locking/lockdep.c:5049
 lock_acquire+0x26c/0x7cc kernel/locking/lockdep.c:5662
 down_read+0x64/0x308 kernel/locking/rwsem.c:1520
 get_super+0x100/0x1f0 fs/super.c:828
 __invalidate_device+0x28/0x108 block/bdev.c:1005
 nbd_clear_sock_ioctl drivers/block/nbd.c:1455 [inline]
 __nbd_ioctl drivers/block/nbd.c:1482 [inline]
 nbd_ioctl+0x2e8/0xc40 drivers/block/nbd.c:1542
 blkdev_ioctl+0x408/0xb40 block/ioctl.c:620
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585