Hello, When fuzzing the Linux kernel driver v6.0-rc4, the following crash was triggered. HEAD commit: 7e18e42e4b280c85b76967a9106a13ca61c16179 git tree: upstream kernel config: https://pastebin.com/raw/xtrgsXP3 console output: https://pastebin.com/raw/9tabWDtu Sorry for failing to extract the reproducer, and the crash occurred at the moment of disconnecting the midi device. On other versions of Linux, I also triggered this crash. I would appreciate it if you have any idea how to solve this bug. The crash report is as follows: ====================================================== WARNING: possible circular locking dependency detected 6.0.0-rc4+ #20 Not tainted ------------------------------------------------------ kworker/1:7/10868 is trying to acquire lock: ffffffff8e289108 (register_mutex#5){+.+.}-{3:3}, at: snd_rawmidi_free+0x7a/0x190 sound/core/rawmidi.c:1902 but task is already holding lock: ffffffff8e274048 (sound_oss_mutex){+.+.}-{3:3}, at: snd_unregister_oss_device+0x97/0x290 sound/core/sound_oss.c:159 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (sound_oss_mutex){+.+.}-{3:3}: lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x580 kernel/locking/lockdep.c:5631 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x14f/0x1f50 kernel/locking/mutex.c:747 snd_unregister_oss_device+0x97/0x290 sound/core/sound_oss.c:159 snd_rawmidi_dev_disconnect+0x418/0x650 sound/core/rawmidi.c:2043 __snd_device_disconnect.part.0+0x5b/0xc0 sound/core/device.c:63 __snd_device_disconnect sound/core/device.c:61 [inline] snd_device_disconnect_all+0x9b/0xf0 sound/core/device.c:215 snd_card_disconnect+0x306/0x740 sound/core/init.c:530 snd_card_free_when_closed+0x13/0x50 sound/core/init.c:622 f_midi_unbind+0x60/0x120 drivers/usb/gadget/function/f_midi.c:1335 purge_configs_funcs+0x281/0x4e0 drivers/usb/gadget/configfs.c:1274 configfs_composite_bind+0xbd3/0x11c0 drivers/usb/gadget/configfs.c:1426 gadget_bind_driver+0x285/0x860 drivers/usb/gadget/udc/core.c:1495 call_driver_probe drivers/base/dd.c:560 [inline] really_probe+0x249/0xa90 drivers/base/dd.c:639 __driver_probe_device+0x1df/0x4d0 drivers/base/dd.c:778 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:808 __driver_attach+0x1e6/0x420 drivers/base/dd.c:1190 bus_for_each_dev+0x147/0x1d0 drivers/base/bus.c:301 bus_add_driver+0x4c9/0x640 drivers/base/bus.c:618 driver_register+0x1c4/0x330 drivers/base/driver.c:240 usb_gadget_register_driver_owner+0xfb/0x1e0 drivers/usb/gadget/udc/core.c:1560 gadget_dev_desc_UDC_store+0x184/0x220 drivers/usb/gadget/configfs.c:299 flush_write_buffer fs/configfs/file.c:207 [inline] configfs_write_iter+0x2ea/0x480 fs/configfs/file.c:229 call_write_iter include/linux/fs.h:2187 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x9ca/0xd90 fs/read_write.c:578 ksys_write+0x127/0x250 fs/read_write.c:631 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #1 (&rmidi->open_mutex){+.+.}-{3:3}: lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x580 kernel/locking/lockdep.c:5631 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x14f/0x1f50 kernel/locking/mutex.c:747 snd_rawmidi_dev_disconnect+0x60/0x650 sound/core/rawmidi.c:2028 __snd_device_disconnect.part.0+0x5b/0xc0 sound/core/device.c:63 __snd_device_disconnect sound/core/device.c:61 [inline] snd_device_disconnect_all+0x9b/0xf0 sound/core/device.c:215 snd_card_disconnect+0x306/0x740 sound/core/init.c:530 snd_card_free_when_closed+0x13/0x50 sound/core/init.c:622 f_midi_unbind+0x60/0x120 drivers/usb/gadget/function/f_midi.c:1335 purge_configs_funcs+0x281/0x4e0 drivers/usb/gadget/configfs.c:1274 configfs_composite_bind+0xbd3/0x11c0 drivers/usb/gadget/configfs.c:1426 gadget_bind_driver+0x285/0x860 drivers/usb/gadget/udc/core.c:1495 call_driver_probe drivers/base/dd.c:560 [inline] really_probe+0x249/0xa90 drivers/base/dd.c:639 __driver_probe_device+0x1df/0x4d0 drivers/base/dd.c:778 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:808 __driver_attach+0x1e6/0x420 drivers/base/dd.c:1190 bus_for_each_dev+0x147/0x1d0 drivers/base/bus.c:301 bus_add_driver+0x4c9/0x640 drivers/base/bus.c:618 driver_register+0x1c4/0x330 drivers/base/driver.c:240 usb_gadget_register_driver_owner+0xfb/0x1e0 drivers/usb/gadget/udc/core.c:1560 gadget_dev_desc_UDC_store+0x184/0x220 drivers/usb/gadget/configfs.c:299 flush_write_buffer fs/configfs/file.c:207 [inline] configfs_write_iter+0x2ea/0x480 fs/configfs/file.c:229 call_write_iter include/linux/fs.h:2187 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x9ca/0xd90 fs/read_write.c:578 ksys_write+0x127/0x250 fs/read_write.c:631 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #0 (register_mutex#5){+.+.}-{3:3}: check_prev_add+0x165/0x2520 kernel/locking/lockdep.c:3095 check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3829 [inline] __lock_acquire+0x2df7/0x5830 kernel/locking/lockdep.c:5053 lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x580 kernel/locking/lockdep.c:5631 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x14f/0x1f50 kernel/locking/mutex.c:747 snd_rawmidi_free+0x7a/0x190 sound/core/rawmidi.c:1902 __snd_device_free+0x19f/0x230 sound/core/device.c:76 snd_device_free_all+0xef/0x210 sound/core/device.c:233 snd_card_do_free sound/core/init.c:591 [inline] release_card_device+0x70/0x200 sound/core/init.c:145 device_release+0x9f/0x240 drivers/base/core.c:2330 kobject_cleanup lib/kobject.c:673 [inline] kobject_release lib/kobject.c:704 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1be/0x4c0 lib/kobject.c:721 put_device+0x1b/0x30 drivers/base/core.c:3624 klist_next+0x254/0x4a0 lib/klist.c:404 class_dev_iter_next+0x83/0xc0 drivers/base/class.c:311 class_find_device+0x144/0x220 drivers/base/class.c:415 class_find_device_by_devt include/linux/device/class.h:167 [inline] device_destroy+0x79/0xd0 drivers/base/core.c:4299 sound_remove_unit+0x13f/0x1f0 sound/sound_core.c:305 snd_unregister_oss_device+0xe8/0x290 sound/core/sound_oss.c:165 snd_mixer_oss_notify_handler+0x282/0x360 sound/core/oss/mixer_oss.c:1417 snd_card_disconnect+0x2f9/0x740 sound/core/init.c:526 usb_audio_disconnect+0x335/0x800 sound/usb/card.c:930 usb_unbind_interface+0x1bd/0x890 drivers/usb/core/driver.c:458 device_remove drivers/base/dd.c:550 [inline] device_remove+0x11f/0x170 drivers/base/dd.c:542 __device_release_driver drivers/base/dd.c:1249 [inline] device_release_driver_internal+0x1a7/0x360 drivers/base/dd.c:1275 bus_remove_device+0x2e3/0x590 drivers/base/bus.c:529 device_del+0x5d2/0xe80 drivers/base/core.c:3704 usb_disable_device+0x214/0x600 drivers/usb/core/message.c:1419 usb_disconnect+0x285/0x860 drivers/usb/core/hub.c:2235 hub_port_connect drivers/usb/core/hub.c:5197 [inline] hub_port_connect_change drivers/usb/core/hub.c:5497 [inline] port_event drivers/usb/core/hub.c:5653 [inline] hub_event+0x1c1b/0x4260 drivers/usb/core/hub.c:5735 process_one_work+0x9c7/0x1650 kernel/workqueue.c:2289 worker_thread+0x623/0x1070 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 other info that might help us debug this: Chain exists of: register_mutex#5 --> &rmidi->open_mutex --> sound_oss_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sound_oss_mutex); lock(&rmidi->open_mutex); lock(sound_oss_mutex); lock(register_mutex#5); *** DEADLOCK *** 7 locks held by kworker/1:7/10868: #0: ffff88801452b938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff88801452b938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline] #0: ffff88801452b938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1280 [inline] #0: ffff88801452b938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:636 [inline] #0: ffff88801452b938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:663 [inline] #0: ffff88801452b938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x8b0/0x1650 kernel/workqueue.c:2260 #1: ffffc90018367db0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x8e4/0x1650 kernel/workqueue.c:2264 #2: ffff8880164d2190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:835 [inline] #2: ffff8880164d2190 (&dev->mutex){....}-{3:3}, at: hub_event+0x1bc/0x4260 drivers/usb/core/hub.c:5681 #3: ffff888047497190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:835 [inline] #3: ffff888047497190 (&dev->mutex){....}-{3:3}, at: usb_disconnect+0x95/0x860 drivers/usb/core/hub.c:2226 #4: ffff888047493118 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0x23/0x360 drivers/base/dd.c:1272 #5: ffffffff8e2e7f68 (register_mutex#7){+.+.}-{3:3}, at: usb_audio_disconnect+0xe3/0x800 sound/usb/card.c:919 #6: ffffffff8e274048 (sound_oss_mutex){+.+.}-{3:3}, at: snd_unregister_oss_device+0x97/0x290 sound/core/sound_oss.c:159 stack backtrace: CPU: 1 PID: 10868 Comm: kworker/1:7 Not tainted 6.0.0-rc4+ #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Workqueue: usb_hub_wq hub_event Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 check_noncircular+0x26b/0x310 kernel/locking/lockdep.c:2175 check_prev_add+0x165/0x2520 kernel/locking/lockdep.c:3095 check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3829 [inline] __lock_acquire+0x2df7/0x5830 kernel/locking/lockdep.c:5053 lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x580 kernel/locking/lockdep.c:5631 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x14f/0x1f50 kernel/locking/mutex.c:747 snd_rawmidi_free+0x7a/0x190 sound/core/rawmidi.c:1902 __snd_device_free+0x19f/0x230 sound/core/device.c:76 snd_device_free_all+0xef/0x210 sound/core/device.c:233 snd_card_do_free sound/core/init.c:591 [inline] release_card_device+0x70/0x200 sound/core/init.c:145 device_release+0x9f/0x240 drivers/base/core.c:2330 kobject_cleanup lib/kobject.c:673 [inline] kobject_release lib/kobject.c:704 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1be/0x4c0 lib/kobject.c:721 put_device+0x1b/0x30 drivers/base/core.c:3624 klist_next+0x254/0x4a0 lib/klist.c:404 class_dev_iter_next+0x83/0xc0 drivers/base/class.c:311 class_find_device+0x144/0x220 drivers/base/class.c:415 class_find_device_by_devt include/linux/device/class.h:167 [inline] device_destroy+0x79/0xd0 drivers/base/core.c:4299 sound_remove_unit+0x13f/0x1f0 sound/sound_core.c:305 snd_unregister_oss_device+0xe8/0x290 sound/core/sound_oss.c:165 snd_mixer_oss_notify_handler+0x282/0x360 sound/core/oss/mixer_oss.c:1417 snd_card_disconnect+0x2f9/0x740 sound/core/init.c:526 usb_audio_disconnect+0x335/0x800 sound/usb/card.c:930 usb_unbind_interface+0x1bd/0x890 drivers/usb/core/driver.c:458 device_remove drivers/base/dd.c:550 [inline] device_remove+0x11f/0x170 drivers/base/dd.c:542 __device_release_driver drivers/base/dd.c:1249 [inline] device_release_driver_internal+0x1a7/0x360 drivers/base/dd.c:1275 bus_remove_device+0x2e3/0x590 drivers/base/bus.c:529 device_del+0x5d2/0xe80 drivers/base/core.c:3704 usb_disable_device+0x214/0x600 drivers/usb/core/message.c:1419 usb_disconnect+0x285/0x860 drivers/usb/core/hub.c:2235 hub_port_connect drivers/usb/core/hub.c:5197 [inline] hub_port_connect_change drivers/usb/core/hub.c:5497 [inline] port_event drivers/usb/core/hub.c:5653 [inline] hub_event+0x1c1b/0x4260 drivers/usb/core/hub.c:5735 process_one_work+0x9c7/0x1650 kernel/workqueue.c:2289 worker_thread+0x623/0x1070 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 </TASK>
