====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc7-syzkaller-00142-gb711733e89a3 #0 Not tainted ------------------------------------------------------ syz.6.473/8177 is trying to acquire lock: ffff88802635e358 (&disk->open_mutex){+.+.}-{4:4}, at: __del_gendisk+0xf5/0xbd0 block/genhd.c:710 but task is already holding lock: ffff88802635d368 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0x136/0x1e0 block/genhd.c:822 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&set->update_nr_hwq_lock){++++}-{4:4}: down_write+0x92/0x200 kernel/locking/rwsem.c:1577 blk_mq_update_nr_hw_queues+0x32/0xcb0 block/blk-mq.c:5041 nbd_start_device+0x172/0xcd0 drivers/block/nbd.c:1476 nbd_start_device_ioctl drivers/block/nbd.c:1527 [inline] __nbd_ioctl drivers/block/nbd.c:1602 [inline] nbd_ioctl+0x219/0xda0 drivers/block/nbd.c:1642 blkdev_ioctl+0x274/0x6d0 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&nbd->config_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:602 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 refcount_dec_and_mutex_lock+0x51/0xc0 lib/refcount.c:118 nbd_config_put+0x31/0x750 drivers/block/nbd.c:1423 nbd_release+0xb7/0x190 drivers/block/nbd.c:1735 blkdev_put_whole+0xb0/0xf0 block/bdev.c:721 bdev_release+0x47e/0x6d0 block/bdev.c:1144 blkdev_release+0x15/0x20 block/fops.c:684 __fput+0x3ff/0xb70 fs/file_table.c:465 fput_close_sync+0x118/0x260 fs/file_table.c:570 __do_sys_close fs/open.c:1589 [inline] __se_sys_close fs/open.c:1574 [inline] __x64_sys_close+0x8b/0x120 fs/open.c:1574 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&disk->open_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 __mutex_lock_common kernel/locking/mutex.c:602 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 __del_gendisk+0xf5/0xbd0 block/genhd.c:710 del_gendisk+0x13e/0x1e0 block/genhd.c:823 loop_remove drivers/block/loop.c:2083 [inline] loop_control_remove drivers/block/loop.c:2142 [inline] loop_control_ioctl+0x4f1/0x630 drivers/block/loop.c:2180 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 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: &disk->open_mutex --> &nbd->config_lock --> &set->update_nr_hwq_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&set->update_nr_hwq_lock); lock(&nbd->config_lock); lock(&set->update_nr_hwq_lock); lock(&disk->open_mutex); *** DEADLOCK *** 1 lock held by syz.6.473/8177: #0: ffff88802635d368 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0x136/0x1e0 block/genhd.c:822 stack backtrace: CPU: 1 UID: 0 PID: 8177 Comm: syz.6.473 Not tainted 6.16.0-rc7-syzkaller-00142-gb711733e89a3 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 __mutex_lock_common kernel/locking/mutex.c:602 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 __del_gendisk+0xf5/0xbd0 block/genhd.c:710 del_gendisk+0x13e/0x1e0 block/genhd.c:823 loop_remove drivers/block/loop.c:2083 [inline] loop_control_remove drivers/block/loop.c:2142 [inline] loop_control_ioctl+0x4f1/0x630 drivers/block/loop.c:2180 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f23cd38e9a9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f23cb1f6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f23cd5b6160 RCX: 00007f23cd38e9a9 RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 0000000000000008 RBP: 00007f23cd410d69 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f23cd5b6160 R15: 00007ffcb7eb97e8