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=146beb3d100000 kernel config: https://syzkaller.appspot.com/x/.config?x=999be4eb2478ffa5 dashboard link: https://syzkaller.appspot.com/bug?extid=fd9d03311cdce9a9ec36 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+fd9d03311cdce9a9ec36@xxxxxxxxxxxxxxxxxxxxxxxxx INFO: task syz-executor.2:9041 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. syz-executor.2 D28808 9041 350 0x00000004 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 schedule_preempt_disabled+0xc/0x20 kernel/sched/core.c:4312 __mutex_lock_common kernel/locking/mutex.c:1033 [inline] __mutex_lock+0x3e2/0x10a0 kernel/locking/mutex.c:1103 sisusb_open+0xb2/0x4d0 drivers/usb/misc/sisusbvga/sisusb.c:2396 usb_open+0x1df/0x270 drivers/usb/core/file.c:48 chrdev_open+0x266/0x770 fs/char_dev.c:414 do_dentry_open+0x4ff/0x1170 fs/open.c:828 do_open fs/namei.c:3243 [inline] path_openat+0x192c/0x26b0 fs/namei.c:3360 do_filp_open+0x17e/0x3c0 fs/namei.c:3387 do_sys_openat2+0x16f/0x3b0 fs/open.c:1179 do_sys_open fs/open.c:1195 [inline] ksys_open include/linux/syscalls.h:1388 [inline] __do_sys_open fs/open.c:1201 [inline] __se_sys_open fs/open.c:1199 [inline] __x64_sys_open+0x119/0x1c0 fs/open.c:1199 do_syscall_64+0x50/0x90 arch/x86/entry/common.c:359 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x416921 Code: Bad RIP value. RSP: 002b:00007f59455b77a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 000000000050a760 RCX: 0000000000416921 RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00007f59455b77d0 RBP: 000000000078bf00 R08: 0000000000000000 R09: 000000000000000f R10: 0000000000000064 R11: 0000000000000293 R12: 00000000ffffffff R13: 0000000000000c43 R14: 00000000004ce974 R15: 00007f59455b86d4 INFO: task syz-executor.4:9085 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. syz-executor.4 D28808 9085 356 0x00000004 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 schedule_preempt_disabled+0xc/0x20 kernel/sched/core.c:4312 __mutex_lock_common kernel/locking/mutex.c:1033 [inline] __mutex_lock+0x3e2/0x10a0 kernel/locking/mutex.c:1103 sisusb_open+0xb2/0x4d0 drivers/usb/misc/sisusbvga/sisusb.c:2396 usb_open+0x1df/0x270 drivers/usb/core/file.c:48 chrdev_open+0x266/0x770 fs/char_dev.c:414 do_dentry_open+0x4ff/0x1170 fs/open.c:828 do_open fs/namei.c:3243 [inline] path_openat+0x192c/0x26b0 fs/namei.c:3360 do_filp_open+0x17e/0x3c0 fs/namei.c:3387 do_sys_openat2+0x16f/0x3b0 fs/open.c:1179 do_sys_open fs/open.c:1195 [inline] ksys_open include/linux/syscalls.h:1388 [inline] __do_sys_open fs/open.c:1201 [inline] __se_sys_open fs/open.c:1199 [inline] __x64_sys_open+0x119/0x1c0 fs/open.c:1199 do_syscall_64+0x50/0x90 arch/x86/entry/common.c:359 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x416921 Code: Bad RIP value. RSP: 002b:00007f1be57797a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 000000000050a760 RCX: 0000000000416921 RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00007f1be57797d0 RBP: 000000000078bfa0 R08: 0000000000000000 R09: 000000000000000f R10: 0000000000000064 R11: 0000000000000293 R12: 00000000ffffffff R13: 0000000000000c43 R14: 00000000004ce974 R15: 00007f1be577a6d4 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 6 locks held by kworker/0:2/67: #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x82b/0x15f0 kernel/workqueue.c:2240 #1: ffff8881d584fda8 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x85f/0x15f0 kernel/workqueue.c:2244 #2: ffff8881d44b3218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #2: ffff8881d44b3218 (&dev->mutex){....}-{3:3}, at: hub_event+0x1c5/0x4390 drivers/usb/core/hub.c:5522 #3: ffff8881ca88f218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #3: ffff8881ca88f218 (&dev->mutex){....}-{3:3}, at: usb_disconnect.cold+0x43/0x780 drivers/usb/core/hub.c:2208 #4: ffff8881d94371a8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #4: ffff8881d94371a8 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:936 [inline] #4: ffff8881d94371a8 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal drivers/base/dd.c:1141 [inline] #4: ffff8881d94371a8 (&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 1 lock held by in:imklog/248: #0: ffff8881d58874f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:826 2 locks held by agetty/274: #0: ffff8881ce8d2098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc90000a222e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x223/0x1a30 drivers/tty/n_tty.c:2156 6 locks held by kworker/0:8/3410: #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff8881d880ed38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x82b/0x15f0 kernel/workqueue.c:2240 #1: ffff8881d55cfda8 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x85f/0x15f0 kernel/workqueue.c:2244 #2: ffff8881d4413218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #2: ffff8881d4413218 (&dev->mutex){....}-{3:3}, at: hub_event+0x1c5/0x4390 drivers/usb/core/hub.c:5522 #3: ffff8881cbe72218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #3: ffff8881cbe72218 (&dev->mutex){....}-{3:3}, at: usb_disconnect.cold+0x43/0x780 drivers/usb/core/hub.c:2208 #4: ffff8881c75b41a8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #4: ffff8881c75b41a8 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:936 [inline] #4: ffff8881c75b41a8 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal drivers/base/dd.c:1141 [inline] #4: ffff8881c75b41a8 (&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 agetty/5507: #0: ffff8881c6234098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffffc9000e49d2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x223/0x1a30 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.2/9041: #0: ffffffff878ac990 (minor_rwsem){++++}-{3:3}, at: usb_open+0x23/0x270 drivers/usb/core/file.c:39 #1: ffff8881cd53b0d0 (&(sisusb->lock)){+.+.}-{3:3}, at: sisusb_open+0xb2/0x4d0 drivers/usb/misc/sisusbvga/sisusb.c:2396 2 locks held by syz-executor.4/9081: #0: ffffffff878ac990 (minor_rwsem){++++}-{3:3}, at: usb_open+0x23/0x270 drivers/usb/core/file.c:39 #1: ffff8881cd53b0d0 (&(sisusb->lock)){+.+.}-{3:3}, at: sisusb_open+0xb2/0x4d0 drivers/usb/misc/sisusbvga/sisusb.c:2396 2 locks held by syz-executor.4/9085: #0: ffffffff878ac990 (minor_rwsem){++++}-{3:3}, at: usb_open+0x23/0x270 drivers/usb/core/file.c:39 #1: ffff8881cd53b0d0 (&(sisusb->lock)){+.+.}-{3:3}, at: sisusb_open+0xb2/0x4d0 drivers/usb/misc/sisusbvga/sisusb.c:2396 ============================================= NMI backtrace for cpu 1 CPU: 1 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 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline] NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline] NMI backtrace for cpu 0 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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