Hello, syzbot found the following crash on: HEAD commit: 768a0741 usb: dwc2: gadget: Remove assigned but never used.. git tree: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing console output: https://syzkaller.appspot.com/x/log.txt?x=17c88f87100000 kernel config: https://syzkaller.appspot.com/x/.config?x=999be4eb2478ffa5 dashboard link: https://syzkaller.appspot.com/bug?extid=4189d5cde8630463053f compiler: gcc (GCC) 10.1.0-syz 20200507 Unfortunately, I don't have any reproducer for this crash yet. IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+4189d5cde8630463053f@xxxxxxxxxxxxxxxxxxxxxxxxx INFO: task kworker/1:4:3051 blocked for more than 143 seconds. Not tainted 5.8.0-rc3-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:4 D23384 3051 2 0x80004000 Workqueue: usb_hub_wq hub_event Call Trace: context_switch kernel/sched/core.c:3453 [inline] __schedule+0x88a/0x1cb0 kernel/sched/core.c:4178 schedule+0xcd/0x2b0 kernel/sched/core.c:4253 rwsem_down_write_slowpath+0x603/0xc60 kernel/locking/rwsem.c:1235 __down_write kernel/locking/rwsem.c:1389 [inline] down_write+0x13c/0x150 kernel/locking/rwsem.c:1532 usb_deregister_dev+0xaa/0x300 drivers/usb/core/file.c:239 sisusb_disconnect+0x5a/0x200 drivers/usb/misc/sisusbvga/sisusb.c:3166 usb_unbind_interface+0x1d8/0x8d0 drivers/usb/core/driver.c:436 __device_release_driver+0x3b7/0x6e0 drivers/base/dd.c:1113 device_release_driver_internal drivers/base/dd.c:1144 [inline] device_release_driver+0x26/0x40 drivers/base/dd.c:1167 bus_remove_device+0x2eb/0x5a0 drivers/base/bus.c:533 device_del+0x47c/0xd20 drivers/base/core.c:2857 usb_disable_device+0x387/0x930 drivers/usb/core/message.c:1245 usb_disconnect.cold+0x27d/0x780 drivers/usb/core/hub.c:2217 hub_port_connect drivers/usb/core/hub.c:5059 [inline] hub_port_connect_change drivers/usb/core/hub.c:5348 [inline] port_event drivers/usb/core/hub.c:5494 [inline] hub_event+0x1c93/0x4390 drivers/usb/core/hub.c:5576 process_one_work+0x94c/0x15f0 kernel/workqueue.c:2269 process_scheduled_works kernel/workqueue.c:2331 [inline] worker_thread+0x82b/0x1120 kernel/workqueue.c:2417 kthread+0x392/0x470 kernel/kthread.c:291 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293 Showing all locks held in the system: 1 lock held by khungtaskd/23: #0: ffffffff873124a0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x264 kernel/locking/lockdep.c:5779 2 locks held by in:imklog/252: #0: ffff8881ca734d70 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:826 #1: ffffffff873a1be0 (fs_reclaim){+.+.}-{0:0}, at: __debug_check_no_obj_freed lib/debugobjects.c:955 [inline] #1: ffffffff873a1be0 (fs_reclaim){+.+.}-{0:0}, at: debug_check_no_obj_freed+0xc7/0x41c lib/debugobjects.c:998 2 locks held by agetty/248: #0: ffff8881d3ea4098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc90000a022e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x223/0x1a30 drivers/tty/n_tty.c:2156 2 locks held by agetty/250: #0: ffff8881c74e4098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc900009f62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x223/0x1a30 drivers/tty/n_tty.c:2156 2 locks held by agetty/253: #0: ffff8881d1e41098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc900009fe2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x223/0x1a30 drivers/tty/n_tty.c:2156 2 locks held by agetty/255: #0: ffff8881ce014098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc900009de2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x223/0x1a30 drivers/tty/n_tty.c:2156 2 locks held by agetty/256: #0: ffff8881ce952098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc900009ee2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x223/0x1a30 drivers/tty/n_tty.c:2156 6 locks held by kworker/1:4/3051: #0: ffff8881d8862938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff8881d8862938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline] #0: ffff8881d8862938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff8881d8862938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline] #0: ffff8881d8862938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff8881d8862938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x82b/0x15f0 kernel/workqueue.c:2240 #1: ffff8881ad5ffda8 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x85f/0x15f0 kernel/workqueue.c:2244 #2: ffff8881d44dc218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #2: ffff8881d44dc218 (&dev->mutex){....}-{3:3}, at: hub_event+0x1c5/0x4390 drivers/usb/core/hub.c:5522 #3: ffff8881ca58e218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #3: ffff8881ca58e218 (&dev->mutex){....}-{3:3}, at: usb_disconnect.cold+0x43/0x780 drivers/usb/core/hub.c:2208 #4: ffff8881c3b4e1a8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #4: ffff8881c3b4e1a8 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:936 [inline] #4: ffff8881c3b4e1a8 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal drivers/base/dd.c:1141 [inline] #4: ffff8881c3b4e1a8 (&dev->mutex){....}-{3:3}, at: device_release_driver+0x1c/0x40 drivers/base/dd.c:1167 #5: ffffffff878ac990 (minor_rwsem){++++}-{3:3}, at: usb_deregister_dev+0xaa/0x300 drivers/usb/core/file.c:239 2 locks held by syz-executor.1/10703: #0: ffffffff878ac990 (minor_rwsem){++++}-{3:3}, at: usb_open+0x23/0x270 drivers/usb/core/file.c:39 #1: ffff8881cb9880d0 (&(sisusb->lock)){+.+.}-{3:3}, at: sisusb_open+0xb2/0x4d0 drivers/usb/misc/sisusbvga/sisusb.c:2396 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 23 Comm: khungtaskd Not tainted 5.8.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xf6/0x16e lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x74/0xb6 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1da/0x1f4 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline] watchdog+0xd6a/0xfd0 kernel/hung_task.c:295 kthread+0x392/0x470 kernel/kthread.c:291 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline] NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline] NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt+0x72/0x90 drivers/acpi/processor_idle.c:111 --- This bug is generated by a bot. 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