====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.2.674/7549 is trying to acquire lock: ffff888107be3a18 (&mdc800->io_lock){+.+.}-{4:4}, at: mdc800_device_open+0x22/0x450 drivers/usb/image/mdc800.c:611 but task is already holding lock: ffffffff8a3395a8 (minor_rwsem#2){++++}-{4:4}, at: usb_open+0x23/0x220 drivers/usb/core/file.c:38 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (minor_rwsem#2){++++}-{4:4}: lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1631 usb_register_dev+0x11d/0x570 drivers/usb/core/file.c:134 mdc800_usb_probe+0x382/0x6d0 drivers/usb/image/mdc800.c:485 usb_probe_interface+0x386/0x9b0 drivers/usb/core/driver.c:399 call_driver_probe drivers/base/dd.c:628 [inline] really_probe+0x241/0xa60 drivers/base/dd.c:706 __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868 driver_probe_device+0x4a/0x140 drivers/base/dd.c:898 __device_attach_driver+0x1df/0x320 drivers/base/dd.c:1026 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1098 device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1153 bus_probe_device+0x64/0x160 drivers/base/bus.c:620 device_add+0x121d/0x1970 drivers/base/core.c:3772 usb_set_configuration+0xd97/0x1c60 drivers/usb/core/message.c:2268 usb_generic_driver_probe+0xa1/0xe0 drivers/usb/core/generic.c:250 usb_probe_device+0xef/0x400 drivers/usb/core/driver.c:293 call_driver_probe drivers/base/dd.c:628 [inline] really_probe+0x241/0xa60 drivers/base/dd.c:706 __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868 driver_probe_device+0x4a/0x140 drivers/base/dd.c:898 __device_attach_driver+0x1df/0x320 drivers/base/dd.c:1026 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1098 device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1153 bus_probe_device+0x64/0x160 drivers/base/bus.c:620 device_add+0x121d/0x1970 drivers/base/core.c:3772 usb_new_device.part.0+0xcc2/0x1686 drivers/usb/core/hub.c:2708 usb_new_device drivers/usb/core/hub.c:5833 [inline] hub_port_connect drivers/usb/core/hub.c:5580 [inline] hub_port_connect_change drivers/usb/core/hub.c:5720 [inline] port_event drivers/usb/core/hub.c:5884 [inline] hub_event.cold+0x51a/0xe9d drivers/usb/core/hub.c:5966 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322 process_scheduled_works kernel/workqueue.c:3405 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x69a/0xc80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (&mdc800->io_lock){+.+.}-{4:4}: check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165 check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 mdc800_device_open+0x22/0x450 drivers/usb/image/mdc800.c:611 usb_open+0x189/0x220 drivers/usb/core/file.c:47 chrdev_open+0x234/0x6a0 fs/char_dev.c:411 do_dentry_open+0x68b/0x14b0 fs/open.c:947 vfs_open+0x82/0x3f0 fs/open.c:1052 do_open fs/namei.c:4700 [inline] path_openat+0x2873/0x4280 fs/namei.c:4863 do_file_open+0x20e/0x430 fs/namei.c:4892 do_sys_openat2+0x10f/0x1e0 fs/open.c:1368 do_sys_open fs/open.c:1374 [inline] __do_sys_openat fs/open.c:1390 [inline] __se_sys_openat fs/open.c:1385 [inline] __x64_sys_openat+0x12d/0x210 fs/open.c:1385 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x10b/0x7f0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(minor_rwsem#2); lock(&mdc800->io_lock); lock(minor_rwsem#2); lock(&mdc800->io_lock); *** DEADLOCK *** 1 lock held by syz.2.674/7549: #0: ffffffff8a3395a8 (minor_rwsem#2){++++}-{4:4}, at: usb_open+0x23/0x220 drivers/usb/core/file.c:38 stack backtrace: CPU: 0 UID: 0 PID: 7549 Comm: syz.2.674 Not tainted syzkaller #0 PREEMPT(lazy) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165 check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 mdc800_device_open+0x22/0x450 drivers/usb/image/mdc800.c:611 usb_open+0x189/0x220 drivers/usb/core/file.c:47 chrdev_open+0x234/0x6a0 fs/char_dev.c:411 do_dentry_open+0x68b/0x14b0 fs/open.c:947 vfs_open+0x82/0x3f0 fs/open.c:1052 do_open fs/namei.c:4700 [inline] path_openat+0x2873/0x4280 fs/namei.c:4863 do_file_open+0x20e/0x430 fs/namei.c:4892 do_sys_openat2+0x10f/0x1e0 fs/open.c:1368 do_sys_open fs/open.c:1374 [inline] __do_sys_openat fs/open.c:1390 [inline] __se_sys_openat fs/open.c:1385 [inline] __x64_sys_openat+0x12d/0x210 fs/open.c:1385 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x10b/0x7f0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f4b4a4ce90e 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:00007f4b48f66b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007f4b48f676c0 RCX: 00007f4b4a4ce90e RDX: 0000000000000002 RSI: 00007f4b48f66c00 RDI: ffffffffffffff9c RBP: 00007f4b4a5a5024 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f4b4a796038 R14: 00007f4b4a795fa0 R15: 00007ffe1209c628 usb 5-1: request USB irq fails (submit_retval=-19).