============================================ WARNING: possible recursive locking detected 4.19.211-syzkaller #0 Not tainted -------------------------------------------- syz-executor.5/3638 is trying to acquire lock: 0000000001c7c9fe (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 but task is already holding lock: 0000000001c7c9fe (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 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 6 locks held by syz-executor.5/3638: #0: 000000006fa99ca7 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x26f/0x310 fs/file.c:767 #1: 000000004b5dbf83 (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2779 [inline] #1: 000000004b5dbf83 (sb_writers#3){.+.+}, at: vfs_write+0x463/0x540 fs/read_write.c:548 #2: 00000000a91d6f02 (&sb->s_type->i_mutex_key#10){+.+.}, at: inode_trylock include/linux/fs.h:768 [inline] #2: 00000000a91d6f02 (&sb->s_type->i_mutex_key#10){+.+.}, at: ext4_file_write_iter+0x21f/0xf20 fs/ext4/file.c:238 #3: 0000000068048c09 (&(&i->lock)->rlock){-.-.}, at: spin_lock include/linux/spinlock.h:329 [inline] #3: 0000000068048c09 (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 drivers/tty/serial/8250/8250_core.c:115 #4: 0000000001c7c9fe (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 #5: 00000000d3a38503 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:293 stack backtrace: CPU: 1 PID: 3638 Comm: syz-executor.5 Not tainted 4.19.211-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1fc/0x2ef lib/dump_stack.c:118 print_deadlock_bug kernel/locking/lockdep.c:1764 [inline] check_deadlock kernel/locking/lockdep.c:1808 [inline] validate_chain kernel/locking/lockdep.c:2404 [inline] __lock_acquire.cold+0x121/0x57e kernel/locking/lockdep.c:3416 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x8c/0xc0 kernel/locking/spinlock.c:152 uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 n_hdlc_send_frames+0x278/0x470 drivers/tty/n_hdlc.c:403 n_hdlc_tty_wakeup+0xa0/0xc0 drivers/tty/n_hdlc.c:479 tty_wakeup+0xd4/0x110 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0x26/0x40 drivers/tty/tty_port.c:50 serial8250_tx_chars+0x490/0xaf0 drivers/tty/serial/8250/8250_port.c:1813 serial8250_handle_irq.part.0+0x31f/0x3d0 drivers/tty/serial/8250/8250_port.c:1900 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1873 [inline] serial8250_default_handle_irq+0xae/0x220 drivers/tty/serial/8250/8250_port.c:1916 serial8250_interrupt+0x101/0x240 drivers/tty/serial/8250/8250_core.c:125 __handle_irq_event_percpu+0x27e/0x8e0 kernel/irq/handle.c:149 handle_irq_event_percpu kernel/irq/handle.c:189 [inline] handle_irq_event+0x102/0x290 kernel/irq/handle.c:206 handle_edge_irq+0x260/0xcf0 kernel/irq/chip.c:800 generic_handle_irq_desc include/linux/irqdesc.h:155 [inline] handle_irq+0x35/0x50 arch/x86/kernel/irq_64.c:87 do_IRQ+0x93/0x1c0 arch/x86/kernel/irq.c:246 common_interrupt+0xf/0xf arch/x86/entry/entry_64.S:670 RIP: 0010:unwind_next_frame+0xa24/0x1400 arch/x86/kernel/unwind_orc.c:508 Code: ff ff 84 c0 0f 84 72 fa ff ff 48 b8 00 00 00 00 00 fc ff df 48 8b 14 24 4c 8b 64 24 68 4c 8b 44 24 30 48 c1 ea 03 80 3c 02 00 <0f> 85 8c 09 00 00 48 8b 54 24 08 4d 89 66 38 48 b8 00 00 00 00 00 RSP: 0018:ffff888046a47210 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffd2 RAX: dffffc0000000000 RBX: 1ffff11008d48e4b RCX: 0000000000000000 RDX: 1ffff11008d48e86 RSI: ffff888046a471a0 RDI: ffff888046a47480 RBP: 0000000000000001 R08: ffffffff8b8fd644 R09: ffffffff8b8fd628 R10: ffff888046a47457 R11: 0000000000074071 R12: ffff888046a47488 R13: ffff888046a4742d R14: ffff888046a473f8 R15: ffffffff8b8fd640 __unwind_start+0x5b8/0x960 arch/x86/kernel/unwind_orc.c:667 unwind_start arch/x86/include/asm/unwind.h:60 [inline] __save_stack_trace+0x72/0x190 arch/x86/kernel/stacktrace.c:43 save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:553 kmem_cache_alloc+0x122/0x370 mm/slab.c:3559 kmem_cache_zalloc include/linux/slab.h:699 [inline] alloc_buffer_head+0x20/0x130 fs/buffer.c:3372 alloc_page_buffers+0x169/0x5c0 fs/buffer.c:830 create_empty_buffers+0x2c/0x760 fs/buffer.c:1528 create_page_buffers+0x212/0x350 fs/buffer.c:1645 __block_write_begin_int+0x22b/0x17b0 fs/buffer.c:1957 ext4_da_write_begin+0x4e1/0x10e0 fs/ext4/inode.c:3109 generic_perform_write+0x1f8/0x4d0 mm/filemap.c:3170 __generic_file_write_iter+0x24b/0x610 mm/filemap.c:3295 ext4_file_write_iter+0x2fe/0xf20 fs/ext4/file.c:272 call_write_iter include/linux/fs.h:1821 [inline] new_sync_write fs/read_write.c:474 [inline] __vfs_write+0x51b/0x770 fs/read_write.c:487 vfs_write+0x1f3/0x540 fs/read_write.c:549 ksys_write+0x12b/0x2a0 fs/read_write.c:599 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7fc424f6c0d9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fc4234de168 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fc42508bf80 RCX: 00007fc424f6c0d9 RDX: 00000000ffffff6a RSI: 0000000020000000 RDI: 000000000000000b RBP: 00007fc424fc7ae9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffc7309cb2f R14: 00007fc4234de300 R15: 0000000000022000 ---------------- Code disassembly (best guess), 2 bytes skipped: 0: 84 c0 test %al,%al 2: 0f 84 72 fa ff ff je 0xfffffa7a 8: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax f: fc ff df 12: 48 8b 14 24 mov (%rsp),%rdx 16: 4c 8b 64 24 68 mov 0x68(%rsp),%r12 1b: 4c 8b 44 24 30 mov 0x30(%rsp),%r8 20: 48 c1 ea 03 shr $0x3,%rdx 24: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) * 28: 0f 85 8c 09 00 00 jne 0x9ba <-- trapping instruction 2e: 48 8b 54 24 08 mov 0x8(%rsp),%rdx 33: 4d 89 66 38 mov %r12,0x38(%r14) 37: 48 rex.W 38: b8 00 00 00 00 mov $0x0,%eax