bisecting fixing commit since cbfa1702aaf69b2311ea1b35e04f113c48368c67 building syzkaller on 1a3f94087169f62f9a5832828f62b4900e98b781 testing commit cbfa1702aaf69b2311ea1b35e04f113c48368c67 with gcc (GCC) 8.1.0 kernel signature: 3880f3a21d65efc4c933bbe20150ed59b39e89ae0a5072581c4f04e2738482bd run #0: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #5: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #6: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #8: crashed: INFO: task hung in hub_port_init run #9: crashed: INFO: task hung in hub_port_init testing current HEAD 27ce4f2a6817e38ca74c643d47a96359f6cc0c1c testing commit 27ce4f2a6817e38ca74c643d47a96359f6cc0c1c with gcc (GCC) 8.1.0 kernel signature: 4f048e2c668ac5f328df7bc205d7c31d5f2c6b2030193ed93a105e1f87be19c4 run #0: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #1: crashed: BUG: unable to handle kernel run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #5: crashed: BUG: unable to handle kernel run #6: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in event_handler run #9: crashed: INFO: task hung in hub_port_init revisions tested: 2, total time: 31m46.721761686s (build: 17m33.64044323s, test: 13m20.974079783s) the crash still happens on HEAD commit msg: Linux 4.14.206 crash: INFO: task hung in hub_port_init vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 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 4.14.206-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:0 D25864 18 2 0x80000000 Workqueue: usb_hub_wq hub_event Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 usb_kill_urb+0x193/0x210 drivers/usb/core/urb.c:691 usb_start_wait_urb+0x1fb/0x260 drivers/usb/core/message.c:62 usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x31b/0x550 drivers/usb/core/message.c:151 hub_port_init+0x6a5/0x2640 drivers/usb/core/hub.c:4555 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+0x12fc/0x3230 drivers/usb/core/hub.c:5274 vhci_hcd vhci_hcd.0: pdev(0) rhport(0) sockfd(3) process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 vhci_hcd: stop threads vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: release socket INFO: task kworker/1:1:23 blocked for more than 140 seconds. vhci_hcd vhci_hcd.0: pdev(4) rhport(0) sockfd(3) vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) Not tainted 4.14.206-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:1 D24928 23 2 0x80000000 Workqueue: usb_hub_wq hub_event vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 usb_kill_urb+0x193/0x210 drivers/usb/core/urb.c:691 vhci_hcd: stop threads vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: release socket usb_start_wait_urb+0x1fb/0x260 drivers/usb/core/message.c:62 vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: pdev(5) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 vhci_hcd: stop threads usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x31b/0x550 drivers/usb/core/message.c:151 hub_port_init+0x6a5/0x2640 drivers/usb/core/hub.c:4555 vhci_hcd: release socket 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+0x12fc/0x3230 drivers/usb/core/hub.c:5274 vhci_hcd: disconnect device process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 vhci_hcd vhci_hcd.0: port 1 already used worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/1:2:3339 blocked for more than 140 seconds. vhci_hcd vhci_hcd.0: pdev(3) rhport(0) sockfd(3) Not tainted 4.14.206-syzkaller #0 vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd vhci_hcd.0: port 1 already used "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 kworker/1:2 D25712 3339 2 0x80000000 Workqueue: usb_hub_wq hub_event vhci_hcd: stop threads Call Trace: vhci_hcd: release socket context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 usb_kill_urb+0x193/0x210 drivers/usb/core/urb.c:691 vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: pdev(1) rhport(0) sockfd(3) usb_start_wait_urb+0x1fb/0x260 drivers/usb/core/message.c:62 vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 vhci_hcd: stop threads vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: release socket vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: pdev(2) rhport(0) sockfd(3) usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x31b/0x550 drivers/usb/core/message.c:151 vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 vhci_hcd: stop threads vhci_hcd: release socket vhci_hcd: disconnect device hub_port_init+0x6a5/0x2640 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+0x12fc/0x3230 drivers/usb/core/hub.c:5274 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/1:3:7093 blocked for more than 140 seconds. Not tainted 4.14.206-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:3 D26856 7093 2 0x80000000 Workqueue: usb_hub_wq hub_event Call Trace: vhci_hcd vhci_hcd.0: port 1 already used context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 usb_kill_urb+0x193/0x210 drivers/usb/core/urb.c:691 vhci_hcd vhci_hcd.0: pdev(0) rhport(0) sockfd(3) usb_start_wait_urb+0x1fb/0x260 drivers/usb/core/message.c:62 vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 vhci_hcd: stop threads vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: release socket vhci_hcd: disconnect device usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x31b/0x550 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(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 hub_port_init+0x6a5/0x2640 drivers/usb/core/hub.c:4555 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+0x12fc/0x3230 drivers/usb/core/hub.c:5274 vhci_hcd: stop threads vhci_hcd vhci_hcd.0: pdev(5) rhport(0) sockfd(3) vhci_hcd: release socket vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 vhci_hcd: disconnect device process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 vhci_hcd: stop threads INFO: task kworker/1:4:7726 blocked for more than 140 seconds. Not tainted 4.14.206-syzkaller #0 vhci_hcd: release socket "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. vhci_hcd: disconnect device kworker/1:4 D24896 7726 2 0x80000000 Workqueue: usb_hub_wq hub_event Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 usb_kill_urb+0x193/0x210 drivers/usb/core/urb.c:691 vhci_hcd vhci_hcd.0: port 1 already used usb_start_wait_urb+0x1fb/0x260 drivers/usb/core/message.c:62 vhci_hcd vhci_hcd.0: pdev(3) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x31b/0x550 drivers/usb/core/message.c:151 vhci_hcd: stop threads vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: release socket vhci_hcd: disconnect device vhci_hcd vhci_hcd.0: pdev(1) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 vhci_hcd: stop threads vhci_hcd vhci_hcd.0: port 1 already used vhci_hcd: release socket hub_port_init+0x6a5/0x2640 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+0x12fc/0x3230 drivers/usb/core/hub.c:5274 vhci_hcd vhci_hcd.0: pdev(2) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 vhci_hcd: stop threads vhci_hcd: release socket worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 vhci_hcd: disconnect device kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 INFO: task kworker/1:5:8036 blocked for more than 140 seconds. Not tainted 4.14.206-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:5 D26336 8036 2 0x80000000 Workqueue: usb_hub_wq hub_event Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x824/0x1ee0 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 usb_kill_urb+0x193/0x210 drivers/usb/core/urb.c:691 usb_start_wait_urb+0x1fb/0x260 drivers/usb/core/message.c:62 usb_internal_control_msg drivers/usb/core/message.c:100 [inline] usb_control_msg+0x31b/0x550 drivers/usb/core/message.c:151 vhci_hcd vhci_hcd.0: port 1 already used hub_port_init+0x6a5/0x2640 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+0x12fc/0x3230 drivers/usb/core/hub.c:5274 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 vhci_hcd vhci_hcd.0: pdev(0) rhport(0) sockfd(3) kthread+0x338/0x400 kernel/kthread.c:232 vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) vhci_hcd: cannot find a urb of seqnum 0 max seqnum 2 vhci_hcd: stop threads ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Showing all locks held in the system: 5 locks held by kworker/1:0/18: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x120/0x3230 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+0x12e1/0x3230 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x145/0x2640 drivers/usb/core/hub.c:4429 5 locks held by kworker/1:1/23: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x120/0x3230 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+0x12e1/0x3230 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x145/0x2640 drivers/usb/core/hub.c:4429 1 lock held by khungtaskd/1037: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4548 5 locks held by kworker/1:2/3339: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x120/0x3230 drivers/usb/core/hub.c:5220 #3: vhci_hcd vhci_hcd.0: port 1 already used (&port_dev->status_lock){+.+.}, at: [] usb_lock_port drivers/usb/core/hub.c:2934 [inline] (&port_dev->status_lock){+.+.}, at: [] hub_port_connect drivers/usb/core/hub.c:4904 [inline] (&port_dev->status_lock){+.+.}, at: [] hub_port_connect_change drivers/usb/core/hub.c:5088 [inline] (&port_dev->status_lock){+.+.}, at: [] port_event drivers/usb/core/hub.c:5194 [inline] (&port_dev->status_lock){+.+.}, at: [] hub_event+0x12e1/0x3230 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x145/0x2640 drivers/usb/core/hub.c:4429 5 locks held by kworker/1:3/7093: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x120/0x3230 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+0x12e1/0x3230 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x145/0x2640 drivers/usb/core/hub.c:4429 5 locks held by kworker/1:4/7726: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x120/0x3230 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+0x12e1/0x3230 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x145/0x2640 drivers/usb/core/hub.c:4429 5 locks held by kworker/1:5/8036: #0: ("usb_hub_wq"){+.+.}, at: [] process_one_work+0x681/0x1620 kernel/workqueue.c:2087 #1: ((&hub->events)){+.+.}, at: [] process_one_work+0x6b4/0x1620 kernel/workqueue.c:2091 #2: (&dev->mutex){....}, at: [] device_lock include/linux/device.h:1081 [inline] #2: (&dev->mutex){....}, at: [] hub_event+0x120/0x3230 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+0x12e1/0x3230 drivers/usb/core/hub.c:5274 #4: (hcd->address0_mutex){+.+.}, at: [] hub_port_init+0x145/0x2640 drivers/usb/core/hub.c:4429 ============================================= vhci_hcd vhci_hcd.0: port 1 already used NMI backtrace for cpu 1 CPU: 1 PID: 1037 Comm: khungtaskd Not tainted 4.14.206-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 vhci_hcd: release socket Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x14b/0x1f1 lib/dump_stack.c:58 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 vhci_hcd vhci_hcd.0: pdev(4) rhport(0) sockfd(3) vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed) nmi_trigger_cpumask_backtrace+0xf5/0x119 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 vhci_hcd: disconnect device trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline] watchdog+0x51b/0xa70 kernel/hung_task.c:274 kthread+0x338/0x400 kernel/kthread.c:232 vhci_hcd: connection closed ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Sending NMI from CPU 1 to CPUs 0: vhci_hcd: stop threads NMI backtrace for cpu 0 CPU: 0 PID: 886 Comm: kworker/u4:4 Not tainted 4.14.206-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: usbip_event event_handler task: ffff8880b426e500 task.stack: ffff8880b4288000 RIP: 0010:io_serial_out+0x62/0x90 drivers/tty/serial/8250/8250_port.c:457 RSP: 0018:ffff8880b428f8f0 EFLAGS: 00000002 RAX: 000000000000005b RBX: ffffffff8a45f100 RCX: 1ffffffff148be27 RDX: 00000000000003f8 RSI: 00000000000003f8 RDI: ffffffff8a45f138 RBP: ffff8880b428f900 R08: 00000000000044a1 R09: ffffffff89557d08 R10: 00000000000000a0 R11: ffff8880b426e500 R12: 000000000000005b R13: ffffffff834ee500 R14: dffffc0000000000 R15: ffffffff89a20608 FS: 0000000000000000(0000) GS:ffff8880ba800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000056005d893ee8 CR3: 00000000a30eb000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: serial_port_out include/linux/serial_core.h:266 [inline] serial8250_console_putchar+0x3d/0x50 drivers/tty/serial/8250/8250_port.c:3206 uart_console_write+0x3c/0xc0 drivers/tty/serial/serial_core.c:1899 serial8250_console_write+0x558/0x860 drivers/tty/serial/8250/8250_port.c:3271 univ8250_console_write+0x4e/0x70 drivers/tty/serial/8250/8250_core.c:596 call_console_drivers kernel/printk/printk.c:1725 [inline] console_unlock+0x862/0xe50 kernel/printk/printk.c:2400 vprintk_emit+0x32f/0x4e0 kernel/printk/printk.c:1923 vprintk_default+0x1a/0x20 kernel/printk/printk.c:1963 vprintk_func+0x49/0x12c kernel/printk/printk_safe.c:401 printk+0x91/0xab kernel/printk/printk.c:1996 vhci_shutdown_connection.cold.6+0x32/0x7a6 drivers/usb/usbip/vhci_hcd.c:1038 event_handler+0x169/0x360 drivers/usb/usbip/usbip_event.c:92 process_one_work+0x74f/0x1620 kernel/workqueue.c:2116 worker_thread+0xcc/0xed0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Code: 31 0f b6 8b d1 00 00 00 48 8d 7b 38 48 ba 00 00 00 00 00 fc ff df d3 e6 48 89 f9 48 c1 e9 03 80 3c 11 00 75 20 03 73 38 89 f2 ee <48> 83 c4 08 5b 5d c3 89 45 f0 89 75 f4 e8 7c 93 35 fe 8b 45 f0