input: HID 0926:3333 as /devices/platform/dummy_hcd.1/usb2/2-1/2-1:0.0/0003:0926:3333.0032/input/input54 keytouch 0003:0926:3333.0032: input,hidraw2: USB HID v0.00 Keyboard [HID 0926:3333] on usb-dummy_hcd.1-1/input0 ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/0:1/10 is trying to acquire lock: ffff888079e492e8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_write_constructor include/linux/rwsem.h:270 [inline] ffff888079e492e8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_flush_buffer+0x1f/0x140 drivers/tty/n_tty.c:349 but task is already holding lock: ffff88801ba820b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:229 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&buf->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:229 tty_ldisc_flush+0x68/0xf0 drivers/tty/tty_ldisc.c:388 __do_SAK+0x3d3/0x520 drivers/tty/tty_io.c:3025 vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275 process_scheduled_works kernel/workqueue.c:3358 [inline] worker_thread+0x5da/0xe40 kernel/workqueue.c:3439 kthread+0x370/0x450 kernel/kthread.c:467 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (console_lock){+.+.}-{0:0}: console_lock+0x7a/0xa0 kernel/printk/printk.c:2896 uart_configure_port drivers/tty/serial/serial_core.c:2519 [inline] serial_core_add_one_port drivers/tty/serial/serial_core.c:3083 [inline] serial_core_register_port+0xeed/0x17a0 drivers/tty/serial/serial_core.c:3305 serial8250_register_8250_port+0x155a/0x2260 drivers/tty/serial/8250/8250_core.c:822 serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480 pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111 call_driver_probe drivers/base/dd.c:583 [inline] really_probe+0x241/0xa60 drivers/base/dd.c:661 __driver_probe_device+0x1de/0x400 drivers/base/dd.c:803 driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:833 __driver_attach+0x2f4/0x6a0 drivers/base/dd.c:1227 bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383 bus_add_driver+0x305/0x5b0 drivers/base/bus.c:715 driver_register+0x1e2/0x360 drivers/base/driver.c:249 serial8250_init+0xcc/0x1b0 drivers/tty/serial/8250/8250_platform.c:317 do_one_initcall+0x11d/0x760 init/main.c:1382 do_initcall_level init/main.c:1444 [inline] do_initcalls init/main.c:1460 [inline] do_basic_setup init/main.c:1479 [inline] kernel_init_freeable+0x6e5/0x7a0 init/main.c:1692 kernel_init+0x1f/0x1e0 init/main.c:1582 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (&port->mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 class_mutex_constructor include/linux/mutex.h:253 [inline] uart_set_termios+0x8e/0x6b0 drivers/tty/serial/serial_core.c:1646 tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341 set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516 tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803 n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982 n_tty_ioctl+0x53/0x370 drivers/tty/n_tty.c:2496 tty_ioctl+0x1204/0x1690 drivers/tty/tty_io.c:2801 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&tty->termios_rwsem){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825 down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1590 class_rwsem_write_constructor include/linux/rwsem.h:270 [inline] n_tty_flush_buffer+0x1f/0x140 drivers/tty/n_tty.c:349 tty_buffer_flush+0x239/0x310 drivers/tty/tty_buffer.c:241 tty_ldisc_flush+0x68/0xf0 drivers/tty/tty_ldisc.c:388 __do_SAK+0x3d3/0x520 drivers/tty/tty_io.c:3025 vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275 process_scheduled_works kernel/workqueue.c:3358 [inline] worker_thread+0x5da/0xe40 kernel/workqueue.c:3439 kthread+0x370/0x450 kernel/kthread.c:467 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 other info that might help us debug this: Chain exists of: &tty->termios_rwsem --> console_lock --> &buf->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&buf->lock); lock(console_lock); lock(&buf->lock); lock(&tty->termios_rwsem); *** DEADLOCK *** 5 locks held by kworker/0:1/10: #0: ffff88813fe63548 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1287/0x1920 kernel/workqueue.c:3250 #1: ffffc900000f7d08 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_one_work+0x93c/0x1920 kernel/workqueue.c:3251 #2: ffffffff8e7d59c0 (console_lock){+.+.}-{0:0}, at: class_console_lock_constructor include/linux/console.h:736 [inline] #2: ffffffff8e7d59c0 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x13/0x320 drivers/tty/vt/vt_ioctl.c:985 #3: ffff888079e490a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref drivers/tty/tty_ldisc.c:263 [inline] #3: ffff888079e490a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x1c/0xf0 drivers/tty/tty_ldisc.c:386 #4: ffff88801ba820b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:229 stack backtrace: CPU: 0 UID: 0 PID: 10 Comm: kworker/0:1 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Workqueue: events vc_SAK 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 kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825 down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1590 class_rwsem_write_constructor include/linux/rwsem.h:270 [inline] n_tty_flush_buffer+0x1f/0x140 drivers/tty/n_tty.c:349 tty_buffer_flush+0x239/0x310 drivers/tty/tty_buffer.c:241 tty_ldisc_flush+0x68/0xf0 drivers/tty/tty_ldisc.c:388 __do_SAK+0x3d3/0x520 drivers/tty/tty_io.c:3025 vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275 process_scheduled_works kernel/workqueue.c:3358 [inline] worker_thread+0x5da/0xe40 kernel/workqueue.c:3439 kthread+0x370/0x450 kernel/kthread.c:467 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 usb 3-1: USB disconnect, device number 11 usb 3-1: new high-speed USB device number 12 using dummy_hcd usb 3-1: config 0 interface 0 altsetting 0 endpoint 0x81 has an invalid bInterval 0, changing to 7 usb 3-1: New USB device found, idVendor=0926, idProduct=3333, bcdDevice= 0.40 usb 3-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0 usb 3-1: config 0 descriptor?? keytouch 0003:0926:3333.0035: fixing up Keytouch IEC report descriptor input: HID 0926:3333 as /devices/platform/dummy_hcd.2/usb3/3-1/3-1:0.0/0003:0926:3333.0035/input/input57 keytouch 0003:0926:3333.0035: input,hidraw0: USB HID v0.00 Keyboard [HID 0926:3333] on usb-dummy_hcd.2-1/input0 usb 4-1: USB disconnect, device number 13 usb 5-1: USB disconnect, device number 13 usb 5-1: new high-speed USB device number 14 using dummy_hcd usb 5-1: config 0 interface 0 altsetting 0 endpoint 0x81 has an invalid bInterval 0, changing to 7 usb 5-1: New USB device found, idVendor=0926, idProduct=3333, bcdDevice= 0.40 usb 5-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0 usb 5-1: config 0 descriptor?? keytouch 0003:0926:3333.0042: fixing up Keytouch IEC report descriptor input: HID 0926:3333 as /devices/platform/dummy_hcd.4/usb5/5-1/5-1:0.0/0003:0926:3333.0042/input/input70 keytouch 0003:0926:3333.0042: input,hidraw3: USB HID v0.00 Keyboard [HID 0926:3333] on usb-dummy_hcd.4-1/input0