block nbd8: NBD_DISCONNECT block nbd8: Send disconnect failed -32 block nbd8: shutting down sockets ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.8.7980/30577 is trying to acquire lock: ffff888027ade940 ((wq_completion)nbd8-recv){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x9c/0x1c0 kernel/workqueue.c:4037 but task is already holding lock: ffff888027a5f260 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_disconnect_and_put+0x26/0x1c0 drivers/block/nbd.c:2293 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&nbd->config_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 refcount_dec_and_mutex_lock+0x51/0x100 lib/refcount.c:118 nbd_config_put+0x31/0x750 drivers/block/nbd.c:1471 recv_work+0x63a/0x8c0 drivers/block/nbd.c:1026 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322 process_scheduled_works kernel/workqueue.c:3405 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 ((work_completion)(&args->work)){+.+.}-{0:0}: lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 process_one_work+0x98e/0x1940 kernel/workqueue.c:3298 process_scheduled_works kernel/workqueue.c:3405 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 ((wq_completion)nbd8-recv){+.+.}-{0:0}: check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165 check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 touch_wq_lockdep_map+0xad/0x1c0 kernel/workqueue.c:4037 __flush_workqueue+0x131/0x1200 kernel/workqueue.c:4079 nbd_disconnect_and_put+0x9b/0x1c0 drivers/block/nbd.c:2301 nbd_genl_disconnect+0x34b/0x4e0 drivers/block/nbd.c:2340 genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2556 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec net/socket.c:775 [inline] __sock_sendmsg net/socket.c:790 [inline] ____sys_sendmsg+0xa4d/0xbe0 net/socket.c:2684 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2738 __sys_sendmsg+0x160/0x210 net/socket.c:2770 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 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: (wq_completion)nbd8-recv --> (work_completion)(&args->work) --> &nbd->config_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&nbd->config_lock); lock((work_completion)(&args->work)); lock(&nbd->config_lock); lock((wq_completion)nbd8-recv); *** DEADLOCK *** 3 locks held by syz.8.7980/30577: #0: ffffffff90b4a748 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217 #1: ffffffff90b4a800 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline] #1: ffffffff90b4a800 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline] #1: ffffffff90b4a800 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:57 [inline] #1: ffffffff90b4a800 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x57b/0x800 net/netlink/genetlink.c:1208 #2: ffff888027a5f260 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_disconnect_and_put+0x26/0x1c0 drivers/block/nbd.c:2293 stack backtrace: CPU: 0 UID: 0 PID: 30577 Comm: syz.8.7980 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165 check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 touch_wq_lockdep_map+0xad/0x1c0 kernel/workqueue.c:4037 __flush_workqueue+0x131/0x1200 kernel/workqueue.c:4079 nbd_disconnect_and_put+0x9b/0x1c0 drivers/block/nbd.c:2301 nbd_genl_disconnect+0x34b/0x4e0 drivers/block/nbd.c:2340 genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2556 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec net/socket.c:775 [inline] __sock_sendmsg net/socket.c:790 [inline] ____sys_sendmsg+0xa4d/0xbe0 net/socket.c:2684 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2738 __sys_sendmsg+0x160/0x210 net/socket.c:2770 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f5bf619e0d9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f5bf710f028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f5bf6426090 RCX: 00007f5bf619e0d9 RDX: 0000000004000810 RSI: 00002000000002c0 RDI: 0000000000000004 RBP: 00007f5bf6235024 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f5bf6426128 R14: 00007f5bf6426090 R15: 00007ffdd0457f58