====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc7-syzkaller-g82af5ea7c611 #0 Not tainted ------------------------------------------------------ kworker/u8:3/42 is trying to acquire lock: ffff0000ca1a5358 (&disk->open_mutex){+.+.}-{4:4}, at: __del_gendisk+0xfc/0x7e0 block/genhd.c:710 but task is already holding lock: ffff0000ca19c988 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xc4/0x14c 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+0x50/0xc0 kernel/locking/rwsem.c:1577 blk_mq_update_nr_hw_queues+0x44/0x10ec block/blk-mq.c:5041 nbd_start_device+0x14c/0x9fc drivers/block/nbd.c:1476 nbd_genl_connect+0xf88/0x158c drivers/block/nbd.c:2218 genl_family_rcv_msg_doit+0x1d8/0x2bc net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x450/0x624 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x220/0x3fc net/netlink/af_netlink.c:2552 genl_rcv+0x38/0x50 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x618/0x830 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x648/0x930 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg net/socket.c:727 [inline] ____sys_sendmsg+0x490/0x7b8 net/socket.c:2566 ___sys_sendmsg+0x204/0x278 net/socket.c:2620 __sys_sendmsg net/socket.c:2652 [inline] __do_sys_sendmsg net/socket.c:2657 [inline] __se_sys_sendmsg net/socket.c:2655 [inline] __arm64_sys_sendmsg+0x184/0x238 net/socket.c:2655 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 -> #1 (&nbd->config_lock){+.+.}-{4:4}: __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:602 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:799 refcount_dec_and_mutex_lock+0x40/0xf0 lib/refcount.c:118 nbd_config_put+0x38/0x614 drivers/block/nbd.c:1423 nbd_release+0xe8/0x130 drivers/block/nbd.c:1735 bdev_release+0x4d8/0x654 block/bdev.c:-1 blkdev_release+0x20/0x34 block/fops.c:684 __fput+0x340/0x75c fs/file_table.c:465 fput_close_sync+0x100/0x224 fs/file_table.c:570 __do_sys_close fs/open.c:1589 [inline] __se_sys_close fs/open.c:1574 [inline] __arm64_sys_close+0x7c/0x118 fs/open.c:1574 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 -> #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+0x1774/0x30a4 kernel/locking/lockdep.c:5240 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5871 __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:602 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:799 __del_gendisk+0xfc/0x7e0 block/genhd.c:710 del_gendisk+0xcc/0x14c block/genhd.c:823 nbd_dev_remove drivers/block/nbd.c:268 [inline] nbd_dev_remove_work+0x48/0xe0 drivers/block/nbd.c:284 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238 process_scheduled_works kernel/workqueue.c:3321 [inline] worker_thread+0x958/0xed8 kernel/workqueue.c:3402 kthread+0x5fc/0x75c kernel/kthread.c:464 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844 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 *** 3 locks held by kworker/u8:3/42: #0: ffff0000c9692148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_one_work+0x63c/0x155c kernel/workqueue.c:3212 #1: ffff800099107bc0 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_one_work+0x6d4/0x155c kernel/workqueue.c:3212 #2: ffff0000ca19c988 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xc4/0x14c block/genhd.c:822 stack backtrace: CPU: 0 UID: 0 PID: 42 Comm: kworker/u8:3 Not tainted 6.16.0-rc7-syzkaller-g82af5ea7c611 #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Workqueue: nbd-del nbd_dev_remove_work Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C) __dump_stack+0x30/0x40 lib/dump_stack.c:94 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_circular_bug+0x324/0x32c kernel/locking/lockdep.c:2046 check_noncircular+0x154/0x174 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+0x1774/0x30a4 kernel/locking/lockdep.c:5240 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5871 __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:602 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:799 __del_gendisk+0xfc/0x7e0 block/genhd.c:710 del_gendisk+0xcc/0x14c block/genhd.c:823 nbd_dev_remove drivers/block/nbd.c:268 [inline] nbd_dev_remove_work+0x48/0xe0 drivers/block/nbd.c:284 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238 process_scheduled_works kernel/workqueue.c:3321 [inline] worker_thread+0x958/0xed8 kernel/workqueue.c:3402 kthread+0x5fc/0x75c kernel/kthread.c:464 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844