kvm: vcpu 0: requested 128 ns lapic timer period limited to 500000 ns 9pnet: Insufficient options for proto=fd kvm: vcpu 0: requested 128 ns lapic timer period limited to 500000 ns ============================================ WARNING: possible recursive locking detected 4.14.290-syzkaller #0 Not tainted -------------------------------------------- syz-executor.1/9916 is trying to acquire lock: (&port_lock_key){-.-.}, at: [] uart_write+0x109/0x560 drivers/tty/serial/serial_core.c:611 but task is already holding lock: (&port_lock_key){-.-.}, at: [] serial8250_handle_irq.part.0+0x20/0x330 drivers/tty/serial/8250/8250_port.c:1891 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&port_lock_key); lock(&port_lock_key); *** DEADLOCK *** May be due to missing lock nesting notation 7 locks held by syz-executor.1/9916: #0: (&f->f_pos_lock){+.+.}, at: [] __fdget_pos+0x1fb/0x2b0 fs/file.c:819 #1: (sb_writers#3){.+.+}, at: [] file_start_write include/linux/fs.h:2714 [inline] #1: (sb_writers#3){.+.+}, at: [] vfs_write+0x3d8/0x4d0 fs/read_write.c:543 #2: (&sb->s_type->i_mutex_key#10){+.+.}, at: [] inode_lock include/linux/fs.h:719 [inline] #2: (&sb->s_type->i_mutex_key#10){+.+.}, at: [] ext4_file_write_iter+0x20f/0xd20 fs/ext4/file.c:239 #3: (rcu_callback){....}, at: [] __rcu_reclaim kernel/rcu/rcu.h:185 [inline] #3: (rcu_callback){....}, at: [] rcu_do_batch kernel/rcu/tree.c:2699 [inline] #3: (rcu_callback){....}, at: [] invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline] #3: (rcu_callback){....}, at: [] __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline] #3: (rcu_callback){....}, at: [] rcu_process_callbacks+0x84e/0x1180 kernel/rcu/tree.c:2946 #4: (&(&i->lock)->rlock){-.-.}, at: [] spin_lock include/linux/spinlock.h:317 [inline] #4: (&(&i->lock)->rlock){-.-.}, at: [] serial8250_interrupt+0x3a/0x210 drivers/tty/serial/8250/8250_core.c:119 #5: (&port_lock_key){-.-.}, at: [] serial8250_handle_irq.part.0+0x20/0x330 drivers/tty/serial/8250/8250_port.c:1891 #6: (&tty->ldisc_sem){++++}, at: [] tty_ldisc_ref+0x1b/0x80 drivers/tty/tty_ldisc.c:305 stack backtrace: CPU: 1 PID: 9916 Comm: syz-executor.1 Not tainted 4.14.290-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b2/0x281 lib/dump_stack.c:58 print_deadlock_bug kernel/locking/lockdep.c:1800 [inline] check_deadlock kernel/locking/lockdep.c:1847 [inline] validate_chain kernel/locking/lockdep.c:2448 [inline] __lock_acquire.cold+0x180/0x97c kernel/locking/lockdep.c:3491 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x8c/0xc0 kernel/locking/spinlock.c:160 uart_write+0x109/0x560 drivers/tty/serial/serial_core.c:611 n_hdlc_send_frames+0x241/0x410 drivers/tty/n_hdlc.c:404 n_hdlc_tty_wakeup+0x95/0xb0 drivers/tty/n_hdlc.c:480 tty_wakeup+0xc3/0xf0 drivers/tty/tty_io.c:533 tty_port_default_wakeup+0x26/0x40 drivers/tty/tty_port.c:49 serial8250_tx_chars+0x3fe/0xc70 drivers/tty/serial/8250/8250_port.c:1828 serial8250_handle_irq.part.0+0x28d/0x330 drivers/tty/serial/8250/8250_port.c:1915 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1888 [inline] serial8250_default_handle_irq+0x8a/0x1f0 drivers/tty/serial/8250/8250_port.c:1931 serial8250_interrupt+0xf3/0x210 drivers/tty/serial/8250/8250_core.c:129 __handle_irq_event_percpu+0xee/0x7f0 kernel/irq/handle.c:147 handle_irq_event_percpu kernel/irq/handle.c:187 [inline] handle_irq_event+0xed/0x240 kernel/irq/handle.c:204 handle_edge_irq+0x224/0xc40 kernel/irq/chip.c:770 generic_handle_irq_desc include/linux/irqdesc.h:159 [inline] handle_irq+0x35/0x50 arch/x86/kernel/irq_64.c:87 do_IRQ+0x93/0x1d0 arch/x86/kernel/irq.c:230 common_interrupt+0x93/0x93 arch/x86/entry/entry_64.S:576 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:779 [inline] RIP: 0010:kmem_cache_free+0x173/0x2b0 mm/slab.c:3759 RSP: 0018:ffff8880ba507e28 EFLAGS: 00000286 ORIG_RAX: ffffffffffffffc8 RAX: 0000000000000007 RBX: ffff8880a4188e00 RCX: 1ffff110154d3947 RDX: 0000000000000000 RSI: ffff8880aa69ca40 RDI: 0000000000000286 RBP: ffff8880b60c9200 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000286 R13: ffffffff8146daa0 R14: ffff8880a4188f18 R15: dffffc0000000000 __rcu_reclaim kernel/rcu/rcu.h:195 [inline] rcu_do_batch kernel/rcu/tree.c:2699 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline] __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline] rcu_process_callbacks+0x780/0x1180 kernel/rcu/tree.c:2946 __do_softirq+0x24d/0x9ff kernel/softirq.c:288 invoke_softirq kernel/softirq.c:368 [inline] irq_exit+0x193/0x240 kernel/softirq.c:409 exiting_irq arch/x86/include/asm/apic.h:638 [inline] smp_apic_timer_interrupt+0x141/0x5e0 arch/x86/kernel/apic/apic.c:1106 apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:793 RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline] RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x50 kernel/kcov.c:60 RSP: 0018:ffff8880ab27f950 EFLAGS: 00000297 ORIG_RAX: ffffffffffffff10 RAX: ffff8880aa69c140 RBX: ffff8880527ee9d8 RCX: 0000000000001000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880527ee9d8 RBP: 0000000000001000 R08: 0000000000001000 R09: ffffea000152c640 R10: ffff8880a38300c0 R11: 0000000000000000 R12: dffffc0000000000 R13: 0000000000000000 R14: ffff8880527ee9d8 R15: 0000000000000000 arch_static_branch arch/x86/include/asm/jump_label.h:36 [inline] static_key_false include/linux/jump_label.h:142 [inline] trace_block_dirty_buffer include/trace/events/block.h:58 [inline] mark_buffer_dirty+0x43/0x480 fs/buffer.c:1151 __block_commit_write.constprop.0.isra.0+0x138/0x200 fs/buffer.c:2111 block_write_end+0x42/0xf0 fs/buffer.c:2189 generic_write_end+0x8d/0x360 fs/buffer.c:2203 ext4_da_write_end+0x50c/0x8e0 fs/ext4/inode.c:3233 generic_perform_write+0x268/0x420 mm/filemap.c:3066 __generic_file_write_iter+0x227/0x590 mm/filemap.c:3180 ext4_file_write_iter+0x276/0xd20 fs/ext4/file.c:270 call_write_iter include/linux/fs.h:1780 [inline] new_sync_write fs/read_write.c:469 [inline] __vfs_write+0x44c/0x630 fs/read_write.c:482 vfs_write+0x17f/0x4d0 fs/read_write.c:544 SYSC_write fs/read_write.c:590 [inline] SyS_write+0xf2/0x210 fs/read_write.c:582 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x7fa07ba0a279 RSP: 002b:00007fa07a33d168 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fa07bb1d120 RCX: 00007fa07ba0a279 RDX: 0000000000032600 RSI: 0000000020000300 RDI: 0000000000000005 RBP: 00007fa07ba64189 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffc71aa936f R14: 00007fa07a33d300 R15: 0000000000022000