====================================================== WARNING: possible circular locking dependency detected 6.15.0-syzkaller-g90b83efa6701-dirty #0 Not tainted ------------------------------------------------------ kworker/u4:2/31 is trying to acquire lock: ffff888000617358 (&disk->open_mutex){+.+.}-{4:4}, at: __del_gendisk+0x129/0x9e0 block/genhd.c:706 but task is already holding lock: ffff88803f055188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&set->update_nr_hwq_lock){++++}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577 blk_mq_update_nr_hw_queues+0x3b/0x14c0 block/blk-mq.c:5041 nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476 nbd_genl_connect+0x1250/0x1930 drivers/block/nbd.c:2203 genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0x21c/0x270 net/socket.c:727 ____sys_sendmsg+0x505/0x830 net/socket.c:2566 ___sys_sendmsg+0x21f/0x2a0 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] __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&nbd->config_lock){+.+.}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 nbd_open+0x2c3/0x5f0 drivers/block/nbd.c:1704 blkdev_get_whole+0x98/0x510 block/bdev.c:730 bdev_open+0x31e/0xd30 block/bdev.c:957 blkdev_open+0x3a8/0x510 block/fops.c:676 do_dentry_open+0xdf0/0x1970 fs/open.c:964 vfs_open+0x3b/0x340 fs/open.c:1094 do_open fs/namei.c:3887 [inline] path_openat+0x2ee5/0x3830 fs/namei.c:4046 do_filp_open+0x1fa/0x410 fs/namei.c:4073 do_sys_openat2+0x121/0x1c0 fs/open.c:1437 do_sys_open fs/open.c:1452 [inline] __do_sys_openat fs/open.c:1468 [inline] __se_sys_openat fs/open.c:1463 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1463 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 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+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 __del_gendisk+0x129/0x9e0 block/genhd.c:706 del_gendisk+0xe8/0x160 block/genhd.c:819 nbd_dev_remove drivers/block/nbd.c:268 [inline] nbd_dev_remove_work+0x47/0xe0 drivers/block/nbd.c:284 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 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/u4:2/31: #0: ffff88801f97e148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline] #0: ffff88801f97e148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3321 #1: ffffc90000527bc0 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline] #1: ffffc90000527bc0 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3321 #2: ffff88803f055188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160 block/genhd.c:818 stack backtrace: CPU: 0 UID: 0 PID: 31 Comm: kworker/u4:2 Not tainted 6.15.0-syzkaller-g90b83efa6701-dirty #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Workqueue: nbd-del nbd_dev_remove_work Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046 check_noncircular+0x134/0x160 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+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 __del_gendisk+0x129/0x9e0 block/genhd.c:706 del_gendisk+0xe8/0x160 block/genhd.c:819 nbd_dev_remove drivers/block/nbd.c:268 [inline] nbd_dev_remove_work+0x47/0xe0 drivers/block/nbd.c:284 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245