====================================================== WARNING: possible circular locking dependency detected 5.16.0-rc2-syzkaller #0 Not tainted ------------------------------------------------------ kworker/1:1/8045 is trying to acquire lock: ffff88801147d0b8 (&buf->lock){+.+.}-{3:3}, at: tty_buffer_flush+0x76/0x2b0 drivers/tty/tty_buffer.c:229 but task is already holding lock: ffffffff8bb70640 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x10/0x310 drivers/tty/vt/vt_ioctl.c:982 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (console_lock){+.+.}-{0:0}: console_lock+0x47/0x80 kernel/printk/printk.c:2524 con_flush_chars drivers/tty/vt/vt.c:3365 [inline] con_flush_chars+0x35/0x90 drivers/tty/vt/vt.c:3357 n_tty_write+0xbe5/0xfd0 drivers/tty/n_tty.c:2305 do_tty_write drivers/tty/tty_io.c:1038 [inline] file_tty_write.constprop.0+0x526/0x910 drivers/tty/tty_io.c:1110 call_write_iter include/linux/fs.h:2162 [inline] new_sync_write+0x429/0x660 fs/read_write.c:503 vfs_write+0x7cd/0xae0 fs/read_write.c:590 ksys_write+0x12d/0x250 fs/read_write.c:643 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #1 (&tty->termios_rwsem){++++}-{3:3}: down_write+0x90/0x150 kernel/locking/rwsem.c:1527 n_tty_flush_buffer+0x1d/0x230 drivers/tty/n_tty.c:369 tty_buffer_flush+0x1f0/0x2b0 drivers/tty/tty_buffer.c:240 tty_ldisc_flush+0x66/0xe0 drivers/tty/tty_ldisc.c:400 tty_port_close_start.part.0+0x22c/0x550 drivers/tty/tty_port.c:602 tty_port_close_start drivers/tty/tty_port.c:646 [inline] tty_port_close+0x46/0x170 drivers/tty/tty_port.c:639 uart_close+0x83/0x210 drivers/tty/serial/serial_core.c:1545 tty_release+0x45e/0x1200 drivers/tty/tty_io.c:1771 __fput+0x286/0x9f0 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:175 [inline] exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:207 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline] syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #0 (&buf->lock){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3063 [inline] check_prevs_add kernel/locking/lockdep.c:3186 [inline] validate_chain kernel/locking/lockdep.c:3801 [inline] __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5027 lock_acquire kernel/locking/lockdep.c:5637 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602 __mutex_lock_common kernel/locking/mutex.c:607 [inline] __mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740 tty_buffer_flush+0x76/0x2b0 drivers/tty/tty_buffer.c:229 tty_ldisc_flush+0x66/0xe0 drivers/tty/tty_ldisc.c:400 __do_SAK.part.0+0xd5/0x390 drivers/tty/tty_io.c:3046 __do_SAK+0x1b/0x30 drivers/tty/tty_io.c:3039 vc_SAK+0x7c/0x310 drivers/tty/vt/vt_ioctl.c:992 process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298 worker_thread+0x658/0x11f0 kernel/workqueue.c:2445 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 other info that might help us debug this: Chain exists of: &buf->lock --> &tty->termios_rwsem --> console_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(console_lock); lock(&tty->termios_rwsem); lock(console_lock); lock(&buf->lock); *** DEADLOCK *** 4 locks held by kworker/1:1/8045: #0: ffff888010c67d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888010c67d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline] #0: ffff888010c67d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline] #0: ffff888010c67d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:635 [inline] #0: ffff888010c67d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:662 [inline] #0: ffff888010c67d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2269 #1: ffffc90003a3fdb0 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2273 #2: ffffffff8bb70640 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x10/0x310 drivers/tty/vt/vt_ioctl.c:982 #3: ffff888015b82098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref drivers/tty/tty_ldisc.c:273 [inline] #3: ffff888015b82098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x18/0xe0 drivers/tty/tty_ldisc.c:398 stack backtrace: CPU: 1 PID: 8045 Comm: kworker/1:1 Not tainted 5.16.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events vc_SAK Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2143 check_prev_add kernel/locking/lockdep.c:3063 [inline] check_prevs_add kernel/locking/lockdep.c:3186 [inline] validate_chain kernel/locking/lockdep.c:3801 [inline] __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5027 lock_acquire kernel/locking/lockdep.c:5637 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602 __mutex_lock_common kernel/locking/mutex.c:607 [inline] __mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740 tty_buffer_flush+0x76/0x2b0 drivers/tty/tty_buffer.c:229 tty_ldisc_flush+0x66/0xe0 drivers/tty/tty_ldisc.c:400 __do_SAK.part.0+0xd5/0x390 drivers/tty/tty_io.c:3046 __do_SAK+0x1b/0x30 drivers/tty/tty_io.c:3039 vc_SAK+0x7c/0x310 drivers/tty/vt/vt_ioctl.c:992 process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298 worker_thread+0x658/0x11f0 kernel/workqueue.c:2445 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 tty tty1: SAK: killed process 6458 (agetty): by session tty tty1: SAK: killed process 6458 (agetty): by controlling tty