bisecting fixing commit since bfb9e5c03076a446b1f4f6a523ddc8d723c907a6
building syzkaller on 36650b4b2c942bc382314dce384d311fbadd1208
testing commit bfb9e5c03076a446b1f4f6a523ddc8d723c907a6 with gcc (GCC) 8.1.0
kernel signature: 1db5ce6eed2aa7ef62e913891077de9567dba3e7bfd6bed28c1ac25cba21899f
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out
testing current HEAD c10b57a567e4333b9fdf60b5ec36de9859263ca2
testing commit c10b57a567e4333b9fdf60b5ec36de9859263ca2 with gcc (GCC) 8.1.0
kernel signature: ac3c2734dec3f900db7d86357e436cb7967f2ca3ed14e28ccd72065842945023
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out
revisions tested: 2, total time: 23m38.962597588s (build: 16m54.693724159s, test: 5m57.484928091s)
the crash still happens on HEAD
commit msg: Linux 4.14.176
crash: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out
IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): hsr0: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): bridge0: link is not ready
BUG: unable to handle kernel NULL pointer dereference at 0000000000000002
8021q: adding VLAN 0 to HW filter on device bond0
IP: writew arch/x86/include/asm/io.h:66 [inline]
IP: mem16_serial_out+0x61/0xa0 drivers/tty/serial/8250/8250_port.c:414
PGD 8ed72067 P4D 8ed72067 PUD 8ed73067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 7306 Comm: syz-executor.2 Not tainted 4.14.176-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88808ddd05c0 task.stack: ffff88808dcd8000
RIP: 0010:writew arch/x86/include/asm/io.h:66 [inline]
RIP: 0010:mem16_serial_out+0x61/0xa0 drivers/tty/serial/8250/8250_port.c:414
RSP: 0018:ffff88808dcdf8a0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffffff8a45ce10 RCX: 1ffffffff148b9ca
RDX: 0000000000000001 RSI: 0000000000000002 RDI: ffffffff8a45ce50
RBP: ffff88808dcdf8b0 R08: ffff88808ddd0e88 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff8a45ce60
R13: ffffffff8a45ce10 R14: ffffffff8a45ce10 R15: ffffffff8a45cedc
FS:  00007f9e790f9700(0000) GS:ffff8880aec00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000002 CR3: 000000008ed7b000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 serial_out drivers/tty/serial/8250/8250.h:120 [inline]
 serial8250_clear_fifos.part.7+0x35/0xb0 drivers/tty/serial/8250/8250_port.c:557
 serial8250_clear_fifos drivers/tty/serial/8250/8250_port.c:556 [inline]
 serial8250_do_startup+0x34c/0x1b10 drivers/tty/serial/8250/8250_port.c:2198
 serial8250_startup+0x39/0x50 drivers/tty/serial/8250/8250_port.c:2415
 uart_port_startup drivers/tty/serial/serial_core.c:231 [inline]
 uart_startup.part.20+0x2a0/0x710 drivers/tty/serial/serial_core.c:270
 uart_startup drivers/tty/serial/serial_core.c:267 [inline]
 uart_set_info drivers/tty/serial/serial_core.c:1010 [inline]
 uart_set_info_user drivers/tty/serial/serial_core.c:1038 [inline]
 uart_ioctl+0x127e/0x2b90 drivers/tty/serial/serial_core.c:1361
 tty_ioctl+0x434/0x1260 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x74/0x80 fs/ioctl.c:692
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45a919
RSP: 002b:00007f9e790f8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a919
RDX: 0000000020000240 RSI: 000000000000541f RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9e790f96d4
R13: 00000000004c5e04 R14: 00000000004dc270 R15: 00000000ffffffff
Code: 0f b6 8b d1 00 00 00 48 8d 7b 40 48 b8 00 00 00 00 00 fc ff df d3 e6 48 89 f9 48 c1 e9 03 80 3c 01 00 75 24 48 63 f6 48 03 73 40 <66> 89 16 48 83 c4 08 5b 5d c3 89 55 f0 89 75 f4 e8 2a c3 37 fe 
IPv6: ADDRCONF(NETDEV_UP): vxcan0: link is not ready
8021q: adding VLAN 0 to HW filter on device bond0
RIP: writew arch/x86/include/asm/io.h:66 [inline] RSP: ffff88808dcdf8a0
RIP: mem16_serial_out+0x61/0xa0 drivers/tty/serial/8250/8250_port.c:414 RSP: ffff88808dcdf8a0
CR2: 0000000000000002
---[ end trace d2407b90ed15a03d ]---
IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready