============================================ WARNING: possible recursive locking detected 4.14.303-syzkaller #0 Not tainted -------------------------------------------- syz-executor.1/9628 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+0x20/0x390 drivers/tty/serial/8250/8250_port.c:1894 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.1/9628: #0: (sb_writers#4){.+.+}, at: [] file_start_write include/linux/fs.h:2714 [inline] #0: (sb_writers#4){.+.+}, at: [] do_sendfile+0x84f/0xb30 fs/read_write.c:1440 #1: (shrinker_rwsem){++++}, at: [] shrink_slab+0x13b/0xb60 mm/vmscan.c:474 #2: (&type->s_umount_key#29){++++}, at: [] trylock_super fs/super.c:402 [inline] #2: (&type->s_umount_key#29){++++}, at: [] super_cache_scan+0x58/0x530 fs/super.c:76 #3: (&(&lru->node[i].lock)->rlock){+.+.}, at: [] spin_lock include/linux/spinlock.h:317 [inline] #3: (&(&lru->node[i].lock)->rlock){+.+.}, at: [] __list_lru_walk_one.isra.0+0x39/0x520 mm/list_lru.c:202 #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+0x20/0x390 drivers/tty/serial/8250/8250_port.c:1894 #6: (&tty->ldisc_sem){++++}, at: [] tty_ldisc_ref+0x1b/0x80 drivers/tty/tty_ldisc.c:305 stack backtrace: CPU: 1 PID: 9628 Comm: syz-executor.1 Not tainted 4.14.303-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/12/2023 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+0x2c7/0x390 drivers/tty/serial/8250/8250_port.c:1918 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1891 [inline] serial8250_default_handle_irq+0x8a/0x1f0 drivers/tty/serial/8250/8250_port.c:1934 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:578 RIP: 0010:queued_spin_trylock include/asm-generic/qspinlock.h:71 [inline] RIP: 0010:do_raw_spin_trylock+0x2d/0xc0 kernel/locking/spinlock_debug.c:119 RSP: 0018:ffff888061997470 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffc8 RAX: 0000000000000000 RBX: ffff88808e3ef0c0 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff818bbf47 RDI: ffff88808e3ef0c0 RBP: ffff88808e3ef120 R08: 0000000000000001 R09: 0000000000000004 R10: 0000000000000000 R11: ffff8880a3ac4580 R12: ffff8880a44b8478 R13: 0000000000000003 R14: ffff88808e3ef0c0 R15: ffff8880a44b8478 __raw_spin_trylock include/linux/spinlock_api_smp.h:89 [inline] _raw_spin_trylock+0x18/0x70 kernel/locking/spinlock.c:136 spin_trylock include/linux/spinlock.h:327 [inline] dentry_lru_isolate+0x2f/0x190 fs/dcache.c:1087 __list_lru_walk_one.isra.0+0x179/0x520 mm/list_lru.c:216 list_lru_shrink_walk include/linux/list_lru.h:173 [inline] prune_dcache_sb+0xc1/0x120 fs/dcache.c:1150 super_cache_scan+0x2f9/0x530 fs/super.c:101 do_shrink_slab mm/vmscan.c:401 [inline] shrink_slab+0x535/0xb60 mm/vmscan.c:504 drop_slab_node+0x2b/0x60 mm/vmscan.c:531 drop_slab+0x39/0x70 mm/vmscan.c:542 drop_caches_sysctl_handler+0xc9/0xe0 fs/drop_caches.c:65 proc_sys_call_handler.isra.0+0x1ba/0x340 fs/proc/proc_sysctl.c:598 __vfs_write+0xe4/0x630 fs/read_write.c:480 __kernel_write+0xf5/0x330 fs/read_write.c:501 write_pipe_buf+0x143/0x1c0 fs/splice.c:797 splice_from_pipe_feed fs/splice.c:502 [inline] __splice_from_pipe+0x326/0x7a0 fs/splice.c:626 splice_from_pipe fs/splice.c:661 [inline] default_file_splice_write+0xc5/0x150 fs/splice.c:809 do_splice_from fs/splice.c:851 [inline] direct_splice_actor+0x115/0x160 fs/splice.c:1018 splice_direct_to_actor+0x27c/0x730 fs/splice.c:973 do_splice_direct+0x164/0x210 fs/splice.c:1061 do_sendfile+0x47f/0xb30 fs/read_write.c:1441 SYSC_sendfile64 fs/read_write.c:1496 [inline] SyS_sendfile64+0x9b/0x110 fs/read_write.c:1488 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x5e/0xd3 RIP: 0033:0x7fb8c8fe80c9 RSP: 002b:00007fb8c755a168 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007fb8c9107f80 RCX: 00007fb8c8fe80c9 RDX: 0000000020002080 RSI: 0000000000000006 RDI: 0000000000000007 RBP: 00007fb8c9043ae9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000870 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffff7632cff R14: 00007fb8c755a300 R15: 0000000000022000