[info] Using makefile-style concurrent boot in runlevel 2. [....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 14.591005][ C1] random: crng init done [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.2' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 35.218060][ T83] usb 1-1: new high-speed USB device number 2 using dummy_hcd [ 35.467949][ T83] usb 1-1: Using ep0 maxpacket: 8 [ 35.588021][ T83] usb 1-1: config 0 has an invalid interface number: 219 but max is 0 [ 35.596537][ T83] usb 1-1: config 0 has no interface number 0 [ 35.603079][ T83] usb 1-1: config 0 interface 219 altsetting 0 endpoint 0xF has an invalid bInterval 0, changing to 7 [ 35.614360][ T83] usb 1-1: config 0 interface 219 altsetting 0 endpoint 0x83 has an invalid bInterval 0, changing to 7 [ 35.625524][ T83] usb 1-1: New USB device found, idVendor=0694, idProduct=0001, bcdDevice=fb.88 [ 35.634581][ T83] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0 [ 35.644362][ T83] usb 1-1: config 0 descriptor?? [ 35.908486][ T83] legousbtower 1-1:0.219: LEGO USB Tower firmware version is 0.0 build 0 [ 35.920180][ T83] legousbtower 1-1:0.219: LEGO USB Tower #-160 now attached to major 180 minor 0 [ 37.188216][ T1721] usb 1-1: LEGO USB Tower reset control request failed [ 37.196244][ T83] usb 1-1: USB disconnect, device number 2 [ 37.206503][ T83] [ 37.208949][ T83] ====================================================== [ 37.215949][ T83] WARNING: possible circular locking dependency detected [ 37.222952][ T83] 5.3.0+ #0 Not tainted [ 37.227260][ T83] ------------------------------------------------------ [ 37.234506][ T83] kworker/1:2/83 is trying to acquire lock: [ 37.240447][ T83] ffffffff87223708 (minor_rwsem){++++}, at: usb_deregister_dev+0x95/0x230 [ 37.249092][ T83] [ 37.249092][ T83] but task is already holding lock: [ 37.256441][ T83] ffffffff872c26e0 (open_disc_mutex){+.+.}, at: tower_disconnect+0x45/0x300 [ 37.265102][ T83] [ 37.265102][ T83] which lock already depends on the new lock. [ 37.265102][ T83] [ 37.275836][ T83] [ 37.275836][ T83] the existing dependency chain (in reverse order) is: [ 37.284832][ T83] [ 37.284832][ T83] -> #1 (open_disc_mutex){+.+.}: [ 37.291933][ T83] __mutex_lock+0x158/0x1360 [ 37.297144][ T83] tower_open+0xce/0x9b0 [ 37.302366][ T83] usb_open+0x1df/0x270 [ 37.307023][ T83] chrdev_open+0x219/0x5c0 [ 37.311945][ T83] do_dentry_open+0x494/0x1120 [ 37.317885][ T83] path_openat+0x1430/0x3f50 [ 37.323172][ T83] do_filp_open+0x1a1/0x280 [ 37.328184][ T83] do_sys_open+0x3c0/0x580 [ 37.333108][ T83] do_syscall_64+0xb7/0x580 [ 37.338118][ T83] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 37.344596][ T83] [ 37.344596][ T83] -> #0 (minor_rwsem){++++}: [ 37.351576][ T83] __lock_acquire+0x1f74/0x3eb0 [ 37.356944][ T83] lock_acquire+0x127/0x320 [ 37.362072][ T83] down_write+0x92/0x150 [ 37.366938][ T83] usb_deregister_dev+0x95/0x230 [ 37.372386][ T83] tower_disconnect+0xa8/0x300 [ 37.378350][ T83] usb_unbind_interface+0x1bd/0x8a0 [ 37.384056][ T83] device_release_driver_internal+0x42f/0x500 [ 37.390626][ T83] bus_remove_device+0x2dc/0x4a0 [ 37.396099][ T83] device_del+0x420/0xb10 [ 37.401059][ T83] usb_disable_device+0x211/0x690 [ 37.406594][ T83] usb_disconnect+0x284/0x8d0 [ 37.411776][ T83] hub_event+0x1454/0x3640 [ 37.416693][ T83] process_one_work+0x92b/0x1530 [ 37.422249][ T83] worker_thread+0x96/0xe20 [ 37.427251][ T83] kthread+0x318/0x420 [ 37.431910][ T83] ret_from_fork+0x24/0x30 [ 37.437143][ T83] [ 37.437143][ T83] other info that might help us debug this: [ 37.437143][ T83] [ 37.448825][ T83] Possible unsafe locking scenario: [ 37.448825][ T83] [ 37.456264][ T83] CPU0 CPU1 [ 37.461751][ T83] ---- ---- [ 37.467128][ T83] lock(open_disc_mutex); [ 37.471526][ T83] lock(minor_rwsem); [ 37.478136][ T83] lock(open_disc_mutex); [ 37.485230][ T83] lock(minor_rwsem); [ 37.489312][ T83] [ 37.489312][ T83] *** DEADLOCK *** [ 37.489312][ T83] [ 37.497544][ T83] 6 locks held by kworker/1:2/83: [ 37.502630][ T83] #0: ffff8881d9099a28 ((wq_completion)usb_hub_wq){+.+.}, at: process_one_work+0x827/0x1530 [ 37.513189][ T83] #1: ffff8881d93cfdd0 ((work_completion)(&hub->events)){+.+.}, at: process_one_work+0x85b/0x1530 [ 37.523978][ T83] #2: ffff8881d5c5f080 (&dev->mutex){....}, at: hub_event+0x17c/0x3640 [ 37.532359][ T83] #3: ffff8881d6455f80 (&dev->mutex){....}, at: usb_disconnect+0x91/0x8d0 [ 37.540931][ T83] #4: ffff8881d6454590 (&dev->mutex){....}, at: device_release_driver_internal+0x23/0x500 [ 37.551071][ T83] #5: ffffffff872c26e0 (open_disc_mutex){+.+.}, at: tower_disconnect+0x45/0x300 [ 37.561415][ T83] [ 37.561415][ T83] stack backtrace: [ 37.567322][ T83] CPU: 1 PID: 83 Comm: kworker/1:2 Not tainted 5.3.0+ #0 [ 37.574360][ T83] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 37.584501][ T83] Workqueue: usb_hub_wq hub_event [ 37.589652][ T83] Call Trace: [ 37.592948][ T83] dump_stack+0xca/0x13e [ 37.597174][ T83] check_noncircular+0x32e/0x3e0 [ 37.602389][ T83] ? save_stack+0x4c/0x80 [ 37.606700][ T83] ? print_circular_bug.isra.0+0x1e0/0x1e0 [ 37.612615][ T83] ? kobject_put+0x18c/0x280 [ 37.617231][ T83] ? usb_deregister_dev+0x89/0x230 [ 37.622436][ T83] ? tower_disconnect+0xa8/0x300 [ 37.627352][ T83] ? usb_unbind_interface+0x1bd/0x8a0 [ 37.632732][ T83] ? graph_lock+0x80/0x180 [ 37.637129][ T83] ? hlock_class+0x120/0x120 [ 37.641700][ T83] ? mark_lock+0xbc/0x1160 [ 37.646096][ T83] __lock_acquire+0x1f74/0x3eb0 [ 37.650927][ T83] ? mark_held_locks+0x9f/0xe0 [ 37.655678][ T83] ? lockdep_hardirqs_on+0x379/0x580 [ 37.660944][ T83] ? mark_held_locks+0xe0/0xe0 [ 37.665715][ T83] lock_acquire+0x127/0x320 [ 37.670198][ T83] ? usb_deregister_dev+0x95/0x230 [ 37.675286][ T83] down_write+0x92/0x150 [ 37.679513][ T83] ? usb_deregister_dev+0x95/0x230 [ 37.684610][ T83] ? down_write_killable_nested+0x180/0x180 [ 37.690486][ T83] ? root_device_unregister+0x80/0x80 [ 37.695839][ T83] usb_deregister_dev+0x95/0x230 [ 37.700986][ T83] tower_disconnect+0xa8/0x300 [ 37.705859][ T83] usb_unbind_interface+0x1bd/0x8a0 [ 37.711384][ T83] ? usb_autoresume_device+0x60/0x60 [ 37.716652][ T83] device_release_driver_internal+0x42f/0x500 [ 37.722826][ T83] bus_remove_device+0x2dc/0x4a0 [ 37.727748][ T83] device_del+0x420/0xb10 [ 37.732071][ T83] ? __device_links_no_driver+0x240/0x240 [ 37.737777][ T83] ? usb_remove_ep_devs+0x3e/0x80 [ 37.742791][ T83] ? remove_intf_ep_devs+0x13f/0x1d0 [ 37.748057][ T83] usb_disable_device+0x211/0x690 [ 37.753062][ T83] usb_disconnect+0x284/0x8d0 [ 37.757728][ T83] hub_event+0x1454/0x3640 [ 37.762164][ T83] ? find_held_lock+0x2d/0x110 [ 37.766907][ T83] ? mark_held_locks+0xe0/0xe0 [ 37.771655][ T83] ? hub_port_debounce+0x260/0x260 [ 37.776753][ T83] ? rcu_read_lock_sched_held+0x9c/0xd0 [ 37.782283][ T83] ? rcu_read_lock_bh_held+0xb0/0xb0 [ 37.787554][ T83] process_one_work