vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd: connection closed vhci_hcd: stop threads vhci_hcd: release socket vhci_hcd: disconnect device INFO: task kworker/1:0:18 blocked for more than 140 seconds. Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:0 D27440 18 2 0x80000000 vhci_hcd vhci_hcd.0: port 1 already used Workqueue: usb_hub_wq hub_event Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x88b/0x1de0 kernel/sched/core.c:3384 schedule+0x8d/0x1b0 kernel/sched/core.c:3428 usb_kill_urb.part.0+0x125/0x190 drivers/usb/core/urb.c:691 vhci_hcd vhci_hcd.0: pdev(3) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:686 vhci_hcd: connection closed usb_start_wait_urb+0x209/0x440 drivers/usb/core/message.c:62 vhci_hcd: stop threads usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x302/0x450 drivers/usb/core/message.c:151 vhci_hcd: release socket hub_port_init+0xfdc/0x2970 drivers/usb/core/hub.c:4555 vhci_hcd: disconnect device hub_port_connect drivers/usb/core/hub.c:4905 [inline] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] port_event drivers/usb/core/hub.c:5194 [inline] hub_event+0x1923/0x3dc0 drivers/usb/core/hub.c:5274 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/0:1:25 blocked for more than 140 seconds. Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/0:1 D27584 25 2 0x80000000 Workqueue: usb_hub_wq hub_event Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x88b/0x1de0 kernel/sched/core.c:3384 schedule+0x8d/0x1b0 kernel/sched/core.c:3428 vhci_hcd vhci_hcd.0: port 1 already used usb_kill_urb.part.0+0x125/0x190 drivers/usb/core/urb.c:691 vhci_hcd vhci_hcd.0: pdev(2) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd vhci_hcd.0: port 1 already used usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:686 vhci_hcd vhci_hcd.0: pdev(4) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd: connection closed usb_start_wait_urb+0x209/0x440 drivers/usb/core/message.c:62 vhci_hcd: stop threads vhci_hcd: release socket vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: port 1 already used usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x302/0x450 drivers/usb/core/message.c:151 vhci_hcd: connection closed vhci_hcd: stop threads vhci_hcd vhci_hcd.0: pdev(1) rhport(0) sockfd(3) hub_port_init+0xfdc/0x2970 drivers/usb/core/hub.c:4555 vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd vhci_hcd.0: port 1 already used hub_port_connect drivers/usb/core/hub.c:4905 [inline] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] port_event drivers/usb/core/hub.c:5194 [inline] hub_event+0x1923/0x3dc0 drivers/usb/core/hub.c:5274 vhci_hcd: release socket vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: pdev(5) rhport(0) sockfd(3) process_one_work+0x793/0x14a0 kernel/workqueue.c:2116 vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd: connection closed vhci_hcd: stop threads vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: connection closed vhci_hcd: release socket vhci_hcd: disconnect device vhci_hcd: stop threads worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250 vhci_hcd: release socket vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: pdev(0) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) kthread+0x30d/0x420 kernel/kthread.c:232 vhci_hcd: connection closed vhci_hcd: stop threads vhci_hcd: release socket ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 vhci_hcd: disconnect device INFO: task kworker/1:2:3484 blocked for more than 140 seconds. vhci_hcd vhci_hcd.0: port 1 already used Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:2 D27224 3484 2 0x80000000 Workqueue: usb_hub_wq hub_event vhci_hcd vhci_hcd.0: pdev(3) rhport(0) sockfd(3) Call Trace: vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd: connection closed vhci_hcd: stop threads context_switch kernel/sched/core.c:2808 [inline] __schedule+0x88b/0x1de0 kernel/sched/core.c:3384 vhci_hcd: release socket vhci_hcd: disconnect device schedule+0x8d/0x1b0 kernel/sched/core.c:3428 usb_kill_urb.part.0+0x125/0x190 drivers/usb/core/urb.c:691 usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:686 usb_start_wait_urb+0x209/0x440 drivers/usb/core/message.c:62 usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x302/0x450 drivers/usb/core/message.c:151 hub_port_init+0xfdc/0x2970 drivers/usb/core/hub.c:4555 hub_port_connect drivers/usb/core/hub.c:4905 [inline] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] port_event drivers/usb/core/hub.c:5194 [inline] hub_event+0x1923/0x3dc0 drivers/usb/core/hub.c:5274 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/1:1:8023 blocked for more than 140 seconds. Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:1 D26720 8023 2 0x80000000 Workqueue: usb_hub_wq hub_event Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x88b/0x1de0 kernel/sched/core.c:3384 schedule+0x8d/0x1b0 kernel/sched/core.c:3428 usb_kill_urb.part.0+0x125/0x190 drivers/usb/core/urb.c:691 vhci_hcd vhci_hcd.0: port 1 already used usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:686 usb_start_wait_urb+0x209/0x440 drivers/usb/core/message.c:62 vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd vhci_hcd.0: pdev(2) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd: connection closed usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x302/0x450 drivers/usb/core/message.c:151 vhci_hcd vhci_hcd.0: pdev(4) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd: connection closed vhci_hcd: stop threads vhci_hcd: release socket vhci_hcd: disconnect device hub_port_init+0xfdc/0x2970 drivers/usb/core/hub.c:4555 vhci_hcd: stop threads hub_port_connect drivers/usb/core/hub.c:4905 [inline] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] port_event drivers/usb/core/hub.c:5194 [inline] hub_event+0x1923/0x3dc0 drivers/usb/core/hub.c:5274 vhci_hcd: release socket vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd vhci_hcd.0: port 1 already used process_one_work+0x793/0x14a0 kernel/workqueue.c:2116 vhci_hcd vhci_hcd.0: pdev(5) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd vhci_hcd.0: pdev(1) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd: connection closed worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250 vhci_hcd: stop threads vhci_hcd: connection closed vhci_hcd: release socket kthread+0x30d/0x420 kernel/kthread.c:232 vhci_hcd: disconnect device vhci_hcd: stop threads ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 vhci_hcd vhci_hcd.0: pdev(0) rhport(0) sockfd(3) INFO: task kworker/1:4:8995 blocked for more than 140 seconds. vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) Not tainted 4.14.212-syzkaller #0 vhci_hcd: release socket vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: disconnect device "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. vhci_hcd vhci_hcd.0: pdev(3) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd: connection closed kworker/1:4 D vhci_hcd: stop threads 28136 8995 2 0x80000000 vhci_hcd: connection closed Workqueue: usb_hub_wq hub_event vhci_hcd: release socket vhci_hcd: disconnect device Call Trace: vhci_hcd: stop threads context_switch kernel/sched/core.c:2808 [inline] __schedule+0x88b/0x1de0 kernel/sched/core.c:3384 vhci_hcd: release socket vhci_hcd: disconnect device schedule+0x8d/0x1b0 kernel/sched/core.c:3428 usb_kill_urb.part.0+0x125/0x190 drivers/usb/core/urb.c:691 usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:686 usb_start_wait_urb+0x209/0x440 drivers/usb/core/message.c:62 usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x302/0x450 drivers/usb/core/message.c:151 hub_port_init+0xfdc/0x2970 drivers/usb/core/hub.c:4555 hub_port_connect drivers/usb/core/hub.c:4905 [inline] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] port_event drivers/usb/core/hub.c:5194 [inline] hub_event+0x1923/0x3dc0 drivers/usb/core/hub.c:5274 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/0:3:9051 blocked for more than 140 seconds. Not tainted 4.14.212-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/0:3 D27608 9051 2 0x80000000 Workqueue: usb_hub_wq hub_event Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x88b/0x1de0 kernel/sched/core.c:3384 schedule+0x8d/0x1b0 kernel/sched/core.c:3428 vhci_hcd vhci_hcd.0: port 1 already used usb_kill_urb.part.0+0x125/0x190 drivers/usb/core/urb.c:691 vhci_hcd vhci_hcd.0: port 1 already used usb_kill_urb+0x7c/0x90 drivers/usb/core/urb.c:686 usb_start_wait_urb+0x209/0x440 drivers/usb/core/message.c:62 vhci_hcd vhci_hcd.0: pdev(4) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd vhci_hcd.0: pdev(2) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x302/0x450 drivers/usb/core/message.c:151 vhci_hcd: connection closed vhci_hcd: connection closed vhci_hcd: stop threads hub_port_init+0xfdc/0x2970 drivers/usb/core/hub.c:4555 vhci_hcd: release socket vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: disconnect device vhci_hcd: stop threads hub_port_connect drivers/usb/core/hub.c:4905 [inline] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] port_event drivers/usb/core/hub.c:5194 [inline] hub_event+0x1923/0x3dc0 drivers/usb/core/hub.c:5274 vhci_hcd: release socket vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: disconnect device process_one_work+0x793/0x14a0 kernel/workqueue.c:2116 vhci_hcd vhci_hcd.0: pdev(1) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: pdev(5) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) vhci_hcd: connection closed vhci_hcd: stop threads vhci_hcd: release socket vhci_hcd: disconnect device vhci_hcd: connection closed vhci_hcd: stop threads vhci_hcd: release socket vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: port 1 already used worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 vhci_hcd vhci_hcd.0: pdev(3) rhport(0) sockfd(3) Showing all locks held in the system: vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) 5 locks held by kworker/1:0/18: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x108/0x3dc0 drivers/usb/core/hub.c:5220 #3: (&port_dev->status_lock){+.+.}, at: [] usb_lock_port drivers/usb/core/hub.c:2934 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect drivers/usb/core/hub.c:4904 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] port_event drivers/usb/core/hub.c:5194 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_event+0x190e/0x3dc0 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x15b/0x2970 drivers/usb/core/hub.c:4429 5 locks held by kworker/0:1/25: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x108/0x3dc0 drivers/usb/core/hub.c:5220 #3: (&port_dev->status_lock){+.+.}, at: [] usb_lock_port drivers/usb/core/hub.c:2934 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect drivers/usb/core/hub.c:4904 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] port_event drivers/usb/core/hub.c:5194 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_event+0x190e/0x3dc0 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x15b/0x2970 drivers/usb/core/hub.c:4429 1 lock held by khungtaskd/1508: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548 5 locks held by kworker/1:2/3484: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x108/0x3dc0 drivers/usb/core/hub.c:5220 #3: (&port_dev->status_lock){+.+.}, at: [] usb_lock_port drivers/usb/core/hub.c:2934 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect drivers/usb/core/hub.c:4904 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] port_event drivers/usb/core/hub.c:5194 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_event+0x190e/0x3dc0 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x15b/0x2970 drivers/usb/core/hub.c:4429 5 locks held by kworker/1:1/8023: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x108/0x3dc0 drivers/usb/core/hub.c:5220 #3: (&port_dev->status_lock){+.+.}, at: [] usb_lock_port drivers/usb/core/hub.c:2934 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect drivers/usb/core/hub.c:4904 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] port_event drivers/usb/core/hub.c:5194 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_event+0x190e/0x3dc0 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x15b/0x2970 drivers/usb/core/hub.c:4429 5 locks held by kworker/1:4/8995: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x108/0x3dc0 drivers/usb/core/hub.c:5220 #3: (&port_dev->status_lock){+.+.}, at: [] usb_lock_port drivers/usb/core/hub.c:2934 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect drivers/usb/core/hub.c:4904 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] port_event drivers/usb/core/hub.c:5194 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_event+0x190e/0x3dc0 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x15b/0x2970 drivers/usb/core/hub.c:4429 5 locks held by kworker/0:3/9051: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x108/0x3dc0 drivers/usb/core/hub.c:5220 #3: (&port_dev->status_lock){+.+.}, at: [] usb_lock_port drivers/usb/core/hub.c:2934 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect drivers/usb/core/hub.c:4904 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] port_event drivers/usb/core/hub.c:5194 [inline] #3: (&port_dev->status_lock){+.+.}, at: [] hub_event+0x190e/0x3dc0 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x15b/0x2970 drivers/usb/core/hub.c:4429 ============================================= vhci_hcd vhci_hcd.0: pdev(0) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed) NMI backtrace for cpu 1 CPU: 1 PID: 1508 Comm: khungtaskd Not tainted 4.14.212-syzkaller #0 vhci_hcd: connection closed Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b2/0x283 lib/dump_stack.c:58 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x13a/0x17f lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline] watchdog+0x5b9/0xb40 kernel/hung_task.c:274 kthread+0x30d/0x420 kernel/kthread.c:232 vhci_hcd: stop threads ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Sending NMI from CPU 1 to CPUs 0: vhci_hcd: release socket NMI backtrace for cpu 0 CPU: 0 PID: 8238 Comm: kworker/u4:3 Not tainted 4.14.212-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: usbip_event event_handler task: ffff8880af31c1c0 task.stack: ffff8880af9e8000 RIP: 0010:io_serial_in+0x60/0x80 drivers/tty/serial/8250/8250_port.c:451 RSP: 0018:ffff8880af9ef950 EFLAGS: 00000002 RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000 RDX: 00000000000003fd RSI: 0000000000000005 RDI: ffffffff8c8bb3b8 RBP: ffffffff8c8bb380 R08: ffffffff8b9a3ee0 R09: 00000000000c0043 R10: ffff8880af31cae8 R11: ffff8880af31c1c0 R12: 0000000000000020 R13: fffffbfff19176b7 R14: fffffbfff1917679 R15: ffffffff8c8bb5ba FS: 0000000000000000(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f0363613fc8 CR3: 00000000a22c9000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: serial_in drivers/tty/serial/8250/8250.h:115 [inline] wait_for_xmitr+0x8a/0x1e0 drivers/tty/serial/8250/8250_port.c:2046 serial8250_console_putchar+0x1b/0x50 drivers/tty/serial/8250/8250_port.c:3205 uart_console_write+0x44/0xd0 drivers/tty/serial/serial_core.c:1899 serial8250_console_write+0x582/0x9d0 drivers/tty/serial/8250/8250_port.c:3271 call_console_drivers kernel/printk/printk.c:1725 [inline] console_unlock+0x99d/0xf20 kernel/printk/printk.c:2400 vprintk_emit+0x224/0x620 kernel/printk/printk.c:1923 vprintk_func+0x58/0x152 kernel/printk/printk_safe.c:401 printk+0x9e/0xbc kernel/printk/printk.c:1996 vhci_shutdown_connection.cold+0xfb/0x84b drivers/usb/usbip/vhci_hcd.c:1046 event_handler+0x1c3/0x4a0 drivers/usb/usbip/usbip_event.c:92 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Code: 30 0f b6 8d d1 00 00 00 48 8d 7d 38 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 d3 e3 80 3c 02 00 75 13 03 5d 38 89 da ec <5b> 0f b6 c0 5d c3 e8 f5 bc 1c fe eb c9 e8 be be 1c fe eb e6 66