serio: Serial port ptm0 ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.79/4564 is trying to acquire lock: ffff88806155fcb8 (kn->active#288){++++}-{0:0}, at: kernfs_remove_by_name_ns+0x91/0x100 fs/kernfs/dir.c:1566 but task is already holding lock: ffffffff8dd6b1c8 (serio_mutex){+.+.}-{3:3}, at: serio_unregister_port+0x2b/0x150 drivers/input/serio/serio.c:707 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (serio_mutex){+.+.}-{3:3}: __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_interruptible_nested+0x17/0x20 kernel/locking/mutex.c:765 drvctl_store+0x2a/0xae0 drivers/input/serio/serio.c:388 kernfs_fop_write_iter+0x3a8/0x500 fs/kernfs/file.c:296 call_write_iter include/linux/fs.h:2179 [inline] new_sync_write fs/read_write.c:507 [inline] vfs_write+0x748/0xd70 fs/read_write.c:594 ksys_write+0x153/0x260 fs/read_write.c:647 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 -> #0 (kn->active#288){++++}-{0:0}: check_prev_add kernel/locking/lockdep.c:3120 [inline] check_prevs_add kernel/locking/lockdep.c:3239 [inline] validate_chain kernel/locking/lockdep.c:3855 [inline] __lock_acquire+0x38f7/0x7d40 kernel/locking/lockdep.c:5120 lock_acquire+0x19f/0x400 kernel/locking/lockdep.c:5737 kernfs_drain fs/kernfs/dir.c:478 [inline] __kernfs_remove+0x5da/0xcb0 fs/kernfs/dir.c:1372 kernfs_remove_by_name_ns+0x91/0x100 fs/kernfs/dir.c:1566 kernfs_remove_by_name include/linux/kernfs.h:598 [inline] remove_files fs/sysfs/group.c:28 [inline] sysfs_remove_group+0xfd/0x290 fs/sysfs/group.c:289 sysfs_remove_groups+0x50/0xa0 fs/sysfs/group.c:313 device_remove_groups drivers/base/core.c:2498 [inline] device_remove_attrs+0xc2/0x140 drivers/base/core.c:2698 device_del+0x637/0xa80 drivers/base/core.c:3614 serio_destroy_port+0x34a/0x470 drivers/input/serio/serio.c:573 serio_unregister_port+0x12c/0x150 drivers/input/serio/serio.c:709 serport_ldisc_read+0x4ec/0x5b0 drivers/input/serio/serport.c:188 iterate_tty_read drivers/tty/tty_io.c:860 [inline] tty_read+0x2af/0x5c0 drivers/tty/tty_io.c:935 call_read_iter include/linux/fs.h:2173 [inline] aio_read+0x33a/0x490 fs/aio.c:1554 __io_submit_one fs/aio.c:-1 [inline] io_submit_one+0x68b/0x1310 fs/aio.c:2013 __do_sys_io_submit fs/aio.c:2072 [inline] __se_sys_io_submit+0x19d/0x310 fs/aio.c:2042 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(serio_mutex); lock(kn->active#288); lock(serio_mutex); lock(kn->active#288); *** DEADLOCK *** 2 locks held by syz.0.79/4564: #0: ffff88802546c098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252 #1: ffffffff8dd6b1c8 (serio_mutex){+.+.}-{3:3}, at: serio_unregister_port+0x2b/0x150 drivers/input/serio/serio.c:707 stack backtrace: CPU: 1 PID: 4564 Comm: syz.0.79 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 check_noncircular+0x2f8/0x400 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3120 [inline] check_prevs_add kernel/locking/lockdep.c:3239 [inline] validate_chain kernel/locking/lockdep.c:3855 [inline] __lock_acquire+0x38f7/0x7d40 kernel/locking/lockdep.c:5120 lock_acquire+0x19f/0x400 kernel/locking/lockdep.c:5737 kernfs_drain fs/kernfs/dir.c:478 [inline] __kernfs_remove+0x5da/0xcb0 fs/kernfs/dir.c:1372 kernfs_remove_by_name_ns+0x91/0x100 fs/kernfs/dir.c:1566 kernfs_remove_by_name include/linux/kernfs.h:598 [inline] remove_files fs/sysfs/group.c:28 [inline] sysfs_remove_group+0xfd/0x290 fs/sysfs/group.c:289 sysfs_remove_groups+0x50/0xa0 fs/sysfs/group.c:313 device_remove_groups drivers/base/core.c:2498 [inline] device_remove_attrs+0xc2/0x140 drivers/base/core.c:2698 device_del+0x637/0xa80 drivers/base/core.c:3614 serio_destroy_port+0x34a/0x470 drivers/input/serio/serio.c:573 serio_unregister_port+0x12c/0x150 drivers/input/serio/serio.c:709 serport_ldisc_read+0x4ec/0x5b0 drivers/input/serio/serport.c:188 iterate_tty_read drivers/tty/tty_io.c:860 [inline] tty_read+0x2af/0x5c0 drivers/tty/tty_io.c:935 call_read_iter include/linux/fs.h:2173 [inline] aio_read+0x33a/0x490 fs/aio.c:1554 __io_submit_one fs/aio.c:-1 [inline] io_submit_one+0x68b/0x1310 fs/aio.c:2013 __do_sys_io_submit fs/aio.c:2072 [inline] __se_sys_io_submit+0x19d/0x310 fs/aio.c:2042 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: 0033:0x7f2d6654fb19 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f2d647a6028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1 RAX: ffffffffffffffda RBX: 00007f2d667d5fa0 RCX: 00007f2d6654fb19 RDX: 0000200000000100 RSI: 000000000000008e RDI: 00007f2d646f7000 RBP: 00007f2d665e7b70 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f2d667d6038 R14: 00007f2d667d5fa0 R15: 00007ffc5a946eb8