Hello, syzbot found the following crash on: HEAD commit: c11d28ab Add linux-next specific files for 20200522 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=17330172100000 kernel config: https://syzkaller.appspot.com/x/.config?x=3f6dbdea4159fb66 dashboard link: https://syzkaller.appspot.com/bug?extid=e3c234427cd464510547 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=122eacba100000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12fffa9a100000 The bug was bisected to: commit 4ef12f7198023c09ad6d25b652bd8748c965c7fa Author: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx> Date: Wed May 13 15:18:40 2020 +0000 kobject: Make sure the parent does not get released before its children bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=146b3d22100000 final crash: https://syzkaller.appspot.com/x/report.txt?x=166b3d22100000 console output: https://syzkaller.appspot.com/x/log.txt?x=126b3d22100000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+e3c234427cd464510547@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 4ef12f719802 ("kobject: Make sure the parent does not get released before its children") usb 1-1: USB disconnect, device number 2 ============================================ WARNING: possible recursive locking detected 5.7.0-rc6-next-20200522-syzkaller #0 Not tainted -------------------------------------------- kworker/1:1/28 is trying to acquire lock: ffffffff8a4f3aa8 (media_devnode_lock){+.+.}-{3:3}, at: media_devnode_release+0x1a/0xe0 drivers/media/mc/mc-devnode.c:53 but task is already holding lock: ffffffff8a4f3aa8 (media_devnode_lock){+.+.}-{3:3}, at: media_devnode_unregister+0x1c/0x69 drivers/media/mc/mc-devnode.c:283 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(media_devnode_lock); lock(media_devnode_lock); *** DEADLOCK *** May be due to missing lock nesting notation 6 locks held by kworker/1:1/28: #0: ffff88821a8e6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: __write_once_size include/linux/compiler.h:303 [inline] #0: ffff88821a8e6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff88821a8e6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline] #0: ffff88821a8e6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff88821a8e6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff88821a8e6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline] #0: ffff88821a8e6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x844/0x16a0 kernel/workqueue.c:2239 #1: ffffc90000de7dc0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x878/0x16a0 kernel/workqueue.c:2243 #2: ffff88809e850218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #2: ffff88809e850218 (&dev->mutex){....}-{3:3}, at: hub_event+0x1b6/0x38f0 drivers/usb/core/hub.c:5522 #3: ffff88809749e218 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:768 [inline] #3: ffff88809749e218 (&dev->mutex){....}-{3:3}, at: usb_disconnect+0x91/0x8d0 drivers/usb/core/hub.c:2208 #4: ffff8880951c01a8 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0x23/0x500 drivers/base/dd.c:1141 #5: ffffffff8a4f3aa8 (media_devnode_lock){+.+.}-{3:3}, at: media_devnode_unregister+0x1c/0x69 drivers/media/mc/mc-devnode.c:283 stack backtrace: CPU: 1 PID: 28 Comm: kworker/1:1 Not tainted 5.7.0-rc6-next-20200522-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: usb_hub_wq hub_event Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x18f/0x20d lib/dump_stack.c:118 print_deadlock_bug kernel/locking/lockdep.c:2391 [inline] check_deadlock kernel/locking/lockdep.c:2432 [inline] validate_chain kernel/locking/lockdep.c:3202 [inline] __lock_acquire.cold+0x240/0x3e2 kernel/locking/lockdep.c:4380 lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4959 __mutex_lock_common kernel/locking/mutex.c:956 [inline] __mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1103 media_devnode_release+0x1a/0xe0 drivers/media/mc/mc-devnode.c:53 device_release+0x71/0x200 drivers/base/core.c:1541 kobject_cleanup lib/kobject.c:701 [inline] kobject_release lib/kobject.c:732 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1c8/0x2f0 lib/kobject.c:749 cdev_device_del+0x69/0x80 fs/char_dev.c:575 media_devnode_unregister+0x2b/0x69 drivers/media/mc/mc-devnode.c:285 media_device_unregister drivers/media/mc/mc-device.c:846 [inline] media_device_unregister+0x3da/0x570 drivers/media/mc/mc-device.c:800 uvc_unregister_video+0x1b6/0x210 drivers/media/usb/uvc/uvc_driver.c:1960 uvc_disconnect+0xbc/0x160 drivers/media/usb/uvc/uvc_driver.c:2270 usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:436 __device_release_driver drivers/base/dd.c:1113 [inline] device_release_driver_internal+0x432/0x500 drivers/base/dd.c:1144 bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:533 device_del+0x481/0xd30 drivers/base/core.c:2839 usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1245 usb_disconnect+0x284/0x8d0 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+0x17ca/0x38f0 drivers/usb/core/hub.c:5576 process_one_work+0x965/0x16a0 kernel/workqueue.c:2268 worker_thread+0x96/0xe20 kernel/workqueue.c:2414 kthread+0x3b5/0x4a0 kernel/kthread.c:291 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351 --- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches
