====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.17/4439 is trying to acquire lock: ffff888023f2fa20 (&mdc800->io_lock){+.+.}-{3:3}, at: mdc800_device_open+0x2a/0x430 drivers/usb/image/mdc800.c:611 but task is already holding lock: ffffffff8cdbb3d0 (minor_rwsem#2){++++}-{3:3}, at: usb_open+0x2c/0x300 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#2){++++}-{3:3}: down_write+0x38/0x60 kernel/locking/rwsem.c:1551 usb_register_dev+0x2a3/0x7f0 drivers/usb/core/file.c:187 mdc800_usb_probe+0xf8a/0x1870 drivers/usb/image/mdc800.c:485 usb_probe_interface+0x5be/0xae0 drivers/usb/core/driver.c:396 call_driver_probe drivers/base/dd.c:-1 [inline] really_probe+0x276/0xc70 drivers/base/dd.c:595 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:775 driver_probe_device+0x4f/0x420 drivers/base/dd.c:805 __device_attach_driver+0x2b0/0x500 drivers/base/dd.c:927 bus_for_each_drv+0x184/0x210 drivers/base/bus.c:429 __device_attach+0x2a7/0x480 drivers/base/dd.c:999 bus_probe_device+0xba/0x1d0 drivers/base/bus.c:489 device_add+0xbcf/0x1050 drivers/base/core.c:3427 usb_set_configuration+0x19d5/0x2030 drivers/usb/core/message.c:2223 usb_generic_driver_probe+0x89/0x150 drivers/usb/core/generic.c:238 usb_probe_device+0x126/0x250 drivers/usb/core/driver.c:293 call_driver_probe drivers/base/dd.c:-1 [inline] really_probe+0x276/0xc70 drivers/base/dd.c:595 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:775 driver_probe_device+0x4f/0x420 drivers/base/dd.c:805 __device_attach_driver+0x2b0/0x500 drivers/base/dd.c:927 bus_for_each_drv+0x184/0x210 drivers/base/bus.c:429 __device_attach+0x2a7/0x480 drivers/base/dd.c:999 bus_probe_device+0xba/0x1d0 drivers/base/bus.c:489 device_add+0xbcf/0x1050 drivers/base/core.c:3427 usb_new_device+0x9f6/0x15d0 drivers/usb/core/hub.c:2632 hub_port_connect drivers/usb/core/hub.c:5497 [inline] hub_port_connect_change drivers/usb/core/hub.c:5637 [inline] port_event drivers/usb/core/hub.c:5799 [inline] hub_event+0x2b8d/0x5260 drivers/usb/core/hub.c:5881 process_one_work+0x867/0xff0 kernel/workqueue.c:2310 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457 kthread+0x42e/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 -> #0 (&mdc800->io_lock){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 mdc800_device_open+0x2a/0x430 drivers/usb/image/mdc800.c:611 usb_open+0x1fe/0x300 drivers/usb/core/file.c:48 chrdev_open+0x585/0x5f0 fs/char_dev.c:414 do_dentry_open+0x7f7/0xf90 fs/open.c:826 do_open fs/namei.c:3616 [inline] path_openat+0x2718/0x2fb0 fs/namei.c:3750 do_filp_open+0x1df/0x400 fs/namei.c:3777 do_sys_openat2+0x14b/0x500 fs/open.c:1255 do_sys_open fs/open.c:1271 [inline] __do_sys_openat fs/open.c:1287 [inline] __se_sys_openat fs/open.c:1282 [inline] __x64_sys_openat+0x135/0x160 fs/open.c:1282 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(minor_rwsem#2); lock(&mdc800->io_lock); lock(minor_rwsem#2); lock(&mdc800->io_lock); *** DEADLOCK *** 1 lock held by syz.0.17/4439: #0: ffffffff8cdbb3d0 (minor_rwsem#2){++++}-{3:3}, at: usb_open+0x2c/0x300 drivers/usb/core/file.c:39 stack backtrace: CPU: 0 PID: 4439 Comm: syz.0.17 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133 check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 mdc800_device_open+0x2a/0x430 drivers/usb/image/mdc800.c:611 usb_open+0x1fe/0x300 drivers/usb/core/file.c:48 chrdev_open+0x585/0x5f0 fs/char_dev.c:414 do_dentry_open+0x7f7/0xf90 fs/open.c:826 do_open fs/namei.c:3616 [inline] path_openat+0x2718/0x2fb0 fs/namei.c:3750 do_filp_open+0x1df/0x400 fs/namei.c:3777 do_sys_openat2+0x14b/0x500 fs/open.c:1255 do_sys_open fs/open.c:1271 [inline] __do_sys_openat fs/open.c:1287 [inline] __se_sys_openat fs/open.c:1282 [inline] __x64_sys_openat+0x135/0x160 fs/open.c:1282 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7fec7eb7b90e Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08 RSP: 002b:00007ffc490d6078 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 000055555cea3500 RCX: 00007fec7eb7b90e RDX: 0000000000000002 RSI: 00007ffc490d6150 RDI: ffffffffffffff9c RBP: 00007fec7ec52024 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fec7ee42fac R14: 00007fec7ee42fa0 R15: 00007fec7ee42fa0