====================================================== WARNING: possible circular locking dependency detected 6.0.0-syzkaller-02734-g0326074ff465 #0 Not tainted ------------------------------------------------------ syz-executor401/4249 is trying to acquire lock: ffff888073f580a8 ((&sq->pending_timer)){+.-.}-{0:0}, at: del_timer_sync+0x33/0x1b0 kernel/time/timer.c:1416 but task is already holding lock: ffffffff9135d270 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline] ffffffff9135d270 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy block/blk-cgroup.c:1519 [inline] ffffffff9135d270 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x181/0x470 block/blk-cgroup.c:1501 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&blkcg->lock){....}-{2:2}: __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:349 [inline] blkg_create+0x461/0x1020 block/blk-cgroup.c:344 blkcg_init_queue+0xb2/0x620 block/blk-cgroup.c:1285 __alloc_disk_node+0x29d/0x650 block/genhd.c:1367 __blk_mq_alloc_disk+0x13b/0x1f0 block/blk-mq.c:3942 floppy_alloc_disk+0x3d/0x390 drivers/block/floppy.c:4514 do_floppy_init drivers/block/floppy.c:4595 [inline] floppy_async_init+0x316/0x21ca drivers/block/floppy.c:4765 async_run_entry_fn+0x98/0x530 kernel/async.c:127 process_one_work+0x991/0x1610 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e4/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 -> #1 (&q->queue_lock){..-.}-{2:2}: __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline] _raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:170 spin_lock_irq include/linux/spinlock.h:374 [inline] throtl_pending_timer_fn+0xf7/0x1690 block/blk-throttle.c:1152 call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers.part.0+0x674/0xa80 kernel/time/timer.c:1790 __run_timers kernel/time/timer.c:1768 [inline] run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1803 __do_softirq+0x1d0/0x9c8 kernel/softirq.c:571 invoke_softirq kernel/softirq.c:445 [inline] __irq_exit_rcu+0x123/0x180 kernel/softirq.c:650 irq_exit_rcu+0x5/0x20 kernel/softirq.c:662 sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1107 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:649 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline] _raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:202 spin_unlock_irq include/linux/spinlock.h:399 [inline] blkcg_deactivate_policy block/blk-cgroup.c:1529 [inline] blkcg_deactivate_policy+0x2f2/0x470 block/blk-cgroup.c:1501 blkcg_iolatency_exit+0x49/0x60 block/blk-iolatency.c:650 rq_qos_exit+0x97/0xf0 block/blk-rq-qos.c:294 del_gendisk+0x762/0xb30 block/genhd.c:642 nbd_dev_remove+0x3c/0xf0 drivers/block/nbd.c:254 process_one_work+0x991/0x1610 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e4/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 -> #0 ((&sq->pending_timer)){+.-.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3829 [inline] __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053 lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 del_timer_sync+0x5b/0x1b0 kernel/time/timer.c:1417 throtl_pd_free+0x15/0x40 block/blk-throttle.c:500 blkcg_deactivate_policy block/blk-cgroup.c:1523 [inline] blkcg_deactivate_policy+0x26c/0x470 block/blk-cgroup.c:1501 blk_throtl_exit+0x8a/0x1a0 block/blk-throttle.c:2337 blkcg_init_queue+0x19b/0x620 block/blk-cgroup.c:1304 __alloc_disk_node+0x29d/0x650 block/genhd.c:1367 __blk_mq_alloc_disk+0x13b/0x1f0 block/blk-mq.c:3942 nbd_dev_add+0x3b2/0xc20 drivers/block/nbd.c:1781 nbd_genl_connect+0x12c5/0x19d0 drivers/block/nbd.c:1964 genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:731 genl_family_rcv_msg net/netlink/genetlink.c:808 [inline] genl_rcv_msg+0x441/0x780 net/netlink/genetlink.c:825 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2540 genl_rcv+0x24/0x40 net/netlink/genetlink.c:836 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x543/0x7f0 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x917/0xe10 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:714 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:734 ____sys_sendmsg+0x712/0x8c0 net/socket.c:2482 ___sys_sendmsg+0x110/0x1b0 net/socket.c:2536 __sys_sendmsg+0xf3/0x1c0 net/socket.c:2565 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd other info that might help us debug this: Chain exists of: (&sq->pending_timer) --> &q->queue_lock --> &blkcg->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&blkcg->lock); lock(&q->queue_lock); lock(&blkcg->lock); lock((&sq->pending_timer)); *** DEADLOCK *** 4 locks held by syz-executor401/4249: #0: ffffffff8d8578b0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:835 #1: ffffffff8d857968 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline] #1: ffffffff8d857968 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x509/0x780 net/netlink/genetlink.c:823 #2: ffff88801d3de778 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline] #2: ffff88801d3de778 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy block/blk-cgroup.c:1512 [inline] #2: ffff88801d3de778 (&q->queue_lock){..-.}-{2:2}, at: blkcg_deactivate_policy+0x9b/0x470 block/blk-cgroup.c:1501 #3: ffffffff9135d270 (&blkcg->lock){....}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline] #3: ffffffff9135d270 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy block/blk-cgroup.c:1519 [inline] #3: ffffffff9135d270 (&blkcg->lock){....}-{2:2}, at: blkcg_deactivate_policy+0x181/0x470 block/blk-cgroup.c:1501 stack backtrace: CPU: 0 PID: 4249 Comm: syz-executor401 Not tainted 6.0.0-syzkaller-02734-g0326074ff465 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3829 [inline] __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053 lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 del_timer_sync+0x5b/0x1b0 kernel/time/timer.c:1417 throtl_pd_free+0x15/0x40 block/blk-throttle.c:500 blkcg_deactivate_policy block/blk-cgroup.c:1523 [inline] blkcg_deactivate_policy+0x26c/0x470 block/blk-cgroup.c:1501 blk_throtl_exit+0x8a/0x1a0 block/blk-throttle.c:2337 blkcg_init_queue+0x19b/0x620 block/blk-cgroup.c:1304 __alloc_disk_node+0x29d/0x650 block/genhd.c:1367 __blk_mq_alloc_disk+0x13b/0x1f0 block/blk-mq.c:3942 nbd_dev_add+0x3b2/0xc20 drivers/block/nbd.c:1781 nbd_genl_connect+0x12c5/0x19d0 drivers/block/nbd.c:1964 genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:731 genl_family_rcv_msg net/netlink/genetlink.c:808 [inline] genl_rcv_msg+0x441/0x780 net/netlink/genetlink.c:825 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2540 genl_rcv+0x24/0x40 net/netlink/genetlink.c:836 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x543/0x7f0 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x917/0xe10 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:714 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:734 ____sys_sendmsg+0x712/0x8c0 net/socket.c:2482 ___sys_sendmsg+0x110/0x1b0 net/socket.c:2536 __sys_sendmsg+0xf3/0x1c0 net/socket.c:2565 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f052a284649 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 18 00 00 90 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 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffd8ee3f028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f052a284649 RDX: 0000000000000000 RSI: 0000000020000380 RDI: 0000000000000004 RBP: 00007ffd8ee3f050 R08: 0000000000000002 R09: 00007ffd8ee3f060 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003 R13: 000000000000000b R14: 00007ffd8ee3f0b0 R15: 00000000000000d9 nbd: failed to add new device