BUG: kernel NULL pointer dereference, address: 0000000000000002 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 9937c067 P4D 9937c067 PUD 95bfa067 PMD 0 Oops: 0002 [#1] PREEMPT SMP KASAN CPU: 0 PID: 8886 Comm: syz-executor205 Not tainted 5.4.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:writeb arch/x86/include/asm/io.h:65 [inline] RIP: 0010:mem_serial_out+0x70/0x90 drivers/tty/serial/8250/8250_port.c:408 Code: e9 00 00 00 49 8d 7c 24 40 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 d3 e3 80 3c 02 00 75 19 48 63 db 49 03 5c 24 40 <44> 88 2b 5b 41 5c 41 5d 5d c3 e8 81 ed cf fd eb c0 e8 da ed cf fd RSP: 0018:ffffc900020978e8 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 0000000000000002 RCX: 0000000000000000 RDX: 1ffffffff181f40e RSI: ffffffff83e28776 RDI: ffffffff8c0fa070 RBP: ffffc90002097900 R08: ffff88809632e400 R09: ffffed10431b01c6 R10: ffffed10431b01c5 R11: ffff888218d80e2b R12: ffffffff8c0fa030 R13: 0000000000000001 R14: ffffc90002097a40 R15: ffffffff8c0fa188 FS: 0000000000af3880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000002 CR3: 000000008d4c9000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: serial_out drivers/tty/serial/8250/8250.h:118 [inline] serial8250_clear_fifos.part.0+0x3a/0xb0 drivers/tty/serial/8250/8250_port.c:557 serial8250_clear_fifos drivers/tty/serial/8250/8250_port.c:556 [inline] serial8250_do_startup+0x426/0x1cf0 drivers/tty/serial/8250/8250_port.c:2121 serial8250_startup+0x62/0x80 drivers/tty/serial/8250/8250_port.c:2329 uart_port_startup drivers/tty/serial/serial_core.c:219 [inline] uart_startup drivers/tty/serial/serial_core.c:258 [inline] uart_startup+0x452/0x980 drivers/tty/serial/serial_core.c:249 uart_set_info drivers/tty/serial/serial_core.c:998 [inline] uart_set_info_user+0x13b4/0x1cf0 drivers/tty/serial/serial_core.c:1023 tty_tiocsserial drivers/tty/tty_io.c:2506 [inline] tty_ioctl+0xf60/0x14f0 drivers/tty/tty_io.c:2648 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x440219 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffd08edd7a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440219 RDX: 0000000020000240 RSI: 000000000000541f RDI: 0000000000000003 RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8 R10: 0000000000401b30 R11: 0000000000000246 R12: 0000000000401aa0 R13: 0000000000401b30 R14: 0000000000000000 R15: 0000000000000000 Modules linked in: CR2: 0000000000000002 ---[ end trace eb54864659d194fb ]--- RIP: 0010:writeb arch/x86/include/asm/io.h:65 [inline] RIP: 0010:mem_serial_out+0x70/0x90 drivers/tty/serial/8250/8250_port.c:408 Code: e9 00 00 00 49 8d 7c 24 40 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 d3 e3 80 3c 02 00 75 19 48 63 db 49 03 5c 24 40 <44> 88 2b 5b 41 5c 41 5d 5d c3 e8 81 ed cf fd eb c0 e8 da ed cf fd RSP: 0018:ffffc900020978e8 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 0000000000000002 RCX: 0000000000000000 RDX: 1ffffffff181f40e RSI: ffffffff83e28776 RDI: ffffffff8c0fa070 RBP: ffffc90002097900 R08: ffff88809632e400 R09: ffffed10431b01c6 R10: ffffed10431b01c5 R11: ffff888218d80e2b R12: ffffffff8c0fa030 R13: 0000000000000001 R14: ffffc90002097a40 R15: ffffffff8c0fa188 FS: 0000000000af3880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000002 CR3: 000000008d4c9000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400