syzbot

======================================================
WARNING: possible circular locking dependency detected
5.4.0-rc1+ #0 Not tainted
------------------------------------------------------
syz-executor.2/25261 is trying to acquire lock:
ffffffff872bd4e0 (open_disc_mutex){+.+.}, at: tower_open+0xce/0x9b0 drivers/usb/misc/legousbtower.c:335

but task is already holding lock:
ffffffff8721edc8 (minor_rwsem){++++}, at: usb_open+0x23/0x270 drivers/usb/core/file.c:39

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (minor_rwsem){++++}:
       down_write+0x92/0x150 kernel/locking/rwsem.c:1534
       usb_deregister_dev+0x95/0x230 drivers/usb/core/file.c:239
       tower_disconnect+0xa8/0x300 drivers/usb/misc/legousbtower.c:951
       usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:423
       __device_release_driver drivers/base/dd.c:1134 [inline]
       device_release_driver_internal+0x42f/0x500 drivers/base/dd.c:1165
       bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:532
       device_del+0x420/0xb20 drivers/base/core.c:2375
       usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
       usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2199
       hub_port_connect drivers/usb/core/hub.c:4949 [inline]
       hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
       port_event drivers/usb/core/hub.c:5359 [inline]
       hub_event+0x1454/0x3640 drivers/usb/core/hub.c:5441
       process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
       worker_thread+0x96/0xe20 kernel/workqueue.c:2415
       kthread+0x318/0x420 kernel/kthread.c:255
       ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

-> #0 (open_disc_mutex){+.+.}:
       check_prev_add kernel/locking/lockdep.c:2476 [inline]
       check_prevs_add kernel/locking/lockdep.c:2581 [inline]
       validate_chain kernel/locking/lockdep.c:2971 [inline]
       __lock_acquire+0x1f74/0x3b60 kernel/locking/lockdep.c:3955
       lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4487
       __mutex_lock_common kernel/locking/mutex.c:956 [inline]
       __mutex_lock+0x158/0x1360 kernel/locking/mutex.c:1103
       tower_open+0xce/0x9b0 drivers/usb/misc/legousbtower.c:335
       usb_open+0x1df/0x270 drivers/usb/core/file.c:48
       chrdev_open+0x219/0x5c0 fs/char_dev.c:414
       do_dentry_open+0x494/0x1120 fs/open.c:797
       do_last fs/namei.c:3408 [inline]
       path_openat+0x1430/0x3ff0 fs/namei.c:3525
       do_filp_open+0x1a1/0x280 fs/namei.c:3555
       do_sys_open+0x3c0/0x580 fs/open.c:1097
       do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:290
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(minor_rwsem);
                               lock(open_disc_mutex);
                               lock(minor_rwsem);
  lock(open_disc_mutex);

 *** DEADLOCK ***

1 lock held by syz-executor.2/25261:
 #0: ffffffff8721edc8 (minor_rwsem){++++}, at: usb_open+0x23/0x270 drivers/usb/core/file.c:39

stack backtrace:
CPU: 0 PID: 25261 Comm: syz-executor.2 Not tainted 5.4.0-rc1+ #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+0xca/0x13e lib/dump_stack.c:113
 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1809
 check_prev_add kernel/locking/lockdep.c:2476 [inline]
 check_prevs_add kernel/locking/lockdep.c:2581 [inline]
 validate_chain kernel/locking/lockdep.c:2971 [inline]
 __lock_acquire+0x1f74/0x3b60 kernel/locking/lockdep.c:3955
 lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4487
 __mutex_lock_common kernel/locking/mutex.c:956 [inline]
 __mutex_lock+0x158/0x1360 kernel/locking/mutex.c:1103
 tower_open+0xce/0x9b0 drivers/usb/misc/legousbtower.c:335
 usb_open+0x1df/0x270 drivers/usb/core/file.c:48
 chrdev_open+0x219/0x5c0 fs/char_dev.c:414
 do_dentry_open+0x494/0x1120 fs/open.c:797
 do_last fs/namei.c:3408 [inline]
 path_openat+0x1430/0x3ff0 fs/namei.c:3525
 do_filp_open+0x1a1/0x280 fs/namei.c:3555
 do_sys_open+0x3c0/0x580 fs/open.c:1097
 do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x413941
Code: 75 14 b8 02 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 19 00 00 c3 48 83 ec 08 e8 0a fa ff ff 48 89 04 24 b8 02 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fa ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007f598eca27a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 6666666666666667 RCX: 0000000000413941
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007f598eca2850
RBP: 000000000075bf20 R08: 000000000000000f R09: 0000000000000000
R10: 00007f598eca39d0 R11: 0000000000000293 R12: 00007f598eca36d4
R13: 00000000004bf17c R14: 00000000004e0578 R15: 00000000ffffffff