RDX: 00000000fffffedf RSI: 0000000020000000 RDI: 0000000000000004 RBP: 0000000000000005 R08: 0000000000000001 R09: 00000000000000c2 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401f50 R13: 0000000000401fe0 R14: 0000000000000000 R15: 0000000000000000 ====================================================== WARNING: possible circular locking dependency detected 4.19.101-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor847/8215 is trying to acquire lock: 000000006ee1b8f8 (console_owner){-...}, at: console_trylock_spinning kernel/printk/printk.c:1669 [inline] 000000006ee1b8f8 (console_owner){-...}, at: vprintk_emit+0x3d5/0x6d0 kernel/printk/printk.c:1936 but task is already holding lock: 00000000181deb8a (&(&port->lock)->rlock){-.-.}, at: pty_write+0xff/0x200 drivers/tty/pty.c:120 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&(&port->lock)->rlock){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152 tty_port_tty_get+0x22/0x90 drivers/tty/tty_port.c:288 tty_port_default_wakeup+0x16/0x40 drivers/tty/tty_port.c:47 tty_port_tty_wakeup+0x57/0x70 drivers/tty/tty_port.c:390 uart_write_wakeup+0x46/0x70 drivers/tty/serial/serial_core.c:103 serial8250_tx_chars+0x495/0xaf0 drivers/tty/serial/8250/8250_port.c:1806 serial8250_handle_irq.part.0+0x261/0x2b0 drivers/tty/serial/8250/8250_port.c:1879 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1865 [inline] serial8250_default_handle_irq+0xc0/0x150 drivers/tty/serial/8250/8250_port.c:1895 serial8250_interrupt+0xfc/0x1e0 drivers/tty/serial/8250/8250_core.c:125 __handle_irq_event_percpu+0x144/0x8f0 kernel/irq/handle.c:149 handle_irq_event_percpu+0x74/0x160 kernel/irq/handle.c:189 handle_irq_event+0xa7/0x134 kernel/irq/handle.c:206 handle_edge_irq+0x25e/0x8d0 kernel/irq/chip.c:797 generic_handle_irq_desc include/linux/irqdesc.h:155 [inline] handle_irq+0x39/0x50 arch/x86/kernel/irq_64.c:87 do_IRQ+0x99/0x1d0 arch/x86/kernel/irq.c:246 ret_from_intr+0x0/0x1e arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] _raw_spin_unlock_irqrestore+0x95/0xe0 kernel/locking/spinlock.c:184 spin_unlock_irqrestore include/linux/spinlock.h:384 [inline] uart_write+0x3a9/0x6e0 drivers/tty/serial/serial_core.c:612 process_output_block drivers/tty/n_tty.c:593 [inline] n_tty_write+0x3f9/0x1140 drivers/tty/n_tty.c:2331 do_tty_write drivers/tty/tty_io.c:960 [inline] tty_write+0x458/0x7a0 drivers/tty/tty_io.c:1044 redirected_tty_write+0xb2/0xc0 drivers/tty/tty_io.c:1065 __vfs_write+0x114/0x810 fs/read_write.c:485 vfs_write+0x20c/0x560 fs/read_write.c:549 ksys_write+0x14f/0x2d0 fs/read_write.c:599 __do_sys_write fs/read_write.c:611 [inline] __se_sys_write fs/read_write.c:608 [inline] __x64_sys_write+0x73/0xb0 fs/read_write.c:608 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&port_lock_key){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152 serial8250_console_write+0x7ca/0x9f0 drivers/tty/serial/8250/8250_port.c:3247 univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:590 call_console_drivers kernel/printk/printk.c:1736 [inline] console_unlock+0xbdf/0x10d0 kernel/printk/printk.c:2429 vprintk_emit+0x280/0x6d0 kernel/printk/printk.c:1937 vprintk_default+0x28/0x30 kernel/printk/printk.c:1979 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398 printk+0xba/0xed kernel/printk/printk.c:2012 register_console+0x77f/0xb90 kernel/printk/printk.c:2745 univ8250_console_init+0x3e/0x4b drivers/tty/serial/8250/8250_core.c:685 console_init+0x4f7/0x761 kernel/printk/printk.c:2831 start_kernel+0x59c/0x825 init/main.c:660 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490 x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #0 (console_owner){-...}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903 console_trylock_spinning kernel/printk/printk.c:1690 [inline] vprintk_emit+0x412/0x6d0 kernel/printk/printk.c:1936 vprintk_default+0x28/0x30 kernel/printk/printk.c:1979 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398 printk+0xba/0xed kernel/printk/printk.c:2012 fail_dump lib/fault-inject.c:44 [inline] should_fail+0x6f1/0x85c lib/fault-inject.c:149 __should_failslab+0x121/0x190 mm/failslab.c:32 should_failslab+0x9/0x14 mm/slab_common.c:1558 slab_pre_alloc_hook mm/slab.h:424 [inline] slab_alloc mm/slab.c:3383 [inline] __do_kmalloc mm/slab.c:3725 [inline] __kmalloc+0x71/0x750 mm/slab.c:3736 kmalloc include/linux/slab.h:520 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:170 [inline] __tty_buffer_request_room+0x1fb/0x5c0 drivers/tty/tty_buffer.c:268 tty_insert_flip_string_fixed_flag+0x93/0x1f0 drivers/tty/tty_buffer.c:313 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0x133/0x200 drivers/tty/pty.c:122 process_output_block drivers/tty/n_tty.c:593 [inline] n_tty_write+0x3f9/0x1140 drivers/tty/n_tty.c:2331 do_tty_write drivers/tty/tty_io.c:960 [inline] tty_write+0x458/0x7a0 drivers/tty/tty_io.c:1044 __vfs_write+0x114/0x810 fs/read_write.c:485 vfs_write+0x20c/0x560 fs/read_write.c:549 ksys_write+0x14f/0x2d0 fs/read_write.c:599 __do_sys_write fs/read_write.c:611 [inline] __se_sys_write fs/read_write.c:608 [inline] __x64_sys_write+0x73/0xb0 fs/read_write.c:608 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: console_owner --> &port_lock_key --> &(&port->lock)->rlock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&port->lock)->rlock); lock(&port_lock_key); lock(&(&port->lock)->rlock); lock(console_owner); *** DEADLOCK *** 5 locks held by syz-executor847/8215: #0: 000000006f51bce1 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000fcf8a3b4 (&tty->atomic_write_lock){+.+.}, at: tty_write_lock+0x23/0x90 drivers/tty/tty_io.c:886 #2: 000000000d2d6305 (&o_tty->termios_rwsem/1){++++}, at: n_tty_write+0x1ab/0x1140 drivers/tty/n_tty.c:2314 #3: 00000000b182e37a (&ldata->output_lock){+.+.}, at: process_output_block drivers/tty/n_tty.c:548 [inline] #3: 00000000b182e37a (&ldata->output_lock){+.+.}, at: n_tty_write+0x52b/0x1140 drivers/tty/n_tty.c:2331 #4: 00000000181deb8a (&(&port->lock)->rlock){-.-.}, at: pty_write+0xff/0x200 drivers/tty/pty.c:120 stack backtrace: CPU: 0 PID: 8215 Comm: syz-executor847 Not tainted 4.19.101-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1221 check_prev_add kernel/locking/lockdep.c:1861 [inline] check_prevs_add kernel/locking/lockdep.c:1974 [inline] validate_chain kernel/locking/lockdep.c:2415 [inline] __lock_acquire+0x2e19/0x49c0 kernel/locking/lockdep.c:3411 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903 console_trylock_spinning kernel/printk/printk.c:1690 [inline] vprintk_emit+0x412/0x6d0 kernel/printk/printk.c:1936 vprintk_default+0x28/0x30 kernel/printk/printk.c:1979 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398 printk+0xba/0xed kernel/printk/printk.c:2012 fail_dump lib/fault-inject.c:44 [inline] should_fail+0x6f1/0x85c lib/fault-inject.c:149 __should_failslab+0x121/0x190 mm/failslab.c:32 should_failslab+0x9/0x14 mm/slab_common.c:1558 slab_pre_alloc_hook mm/slab.h:424 [inline] slab_alloc mm/slab.c:3383 [inline] __do_kmalloc mm/slab.c:3725 [inline] __kmalloc+0x71/0x750 mm/slab.c:3736 kmalloc include/linux/slab.h:520 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:170 [inline] __tty_buffer_request_room+0x1fb/0x5c0 drivers/tty/tty_buffer.c:268 tty_insert_flip_string_fixed_flag+0x93/0x1f0 drivers/tty/tty_buffer.c:313 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0x133/0x200 drivers/tty/pty.c:122 process_output_block drivers/tty/n_tty.c:593 [inline] n_tty_write+0x3f9/0x1140 drivers/tty/n_tty.c:2331 do_tty_write drivers/tty/tty_io.c:960 [inline] tty_write+0x458/0x7a0 drivers/tty/tty_io.c:1044 __vfs_write+0x114/0x810 fs/read_write.c:485 vfs_write+0x20c/0x560 fs/read_write.c:549 ksys_write+0x14f/0x2d0 fs/read_write.c:599 __do_sys_write fs/read_write.c:611 [inline] __se_sys_write fs/read_write.c:608 [inline] __x64_sys_write+0x73/0xb0 fs/read_write.c:608 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x440689 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 3b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffc2c042958 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007ffc2c042970 RCX: 0000000000440689 RDX: 00000000fffffedf RSI: 0000000020000000 RDI: 0000000000000004 RBP: 0000000000000005 R08: 0000000000000001 R09: 00000000000000c2 R10: 00000