bisecting fixing commit since 7d120bf21c05cbe30a679f0feeca884eeaceb069
building syzkaller on 79b211f74b08737aeb4934c6ff69a263b3c38013
testing commit 7d120bf21c05cbe30a679f0feeca884eeaceb069 with gcc (GCC) 8.1.0
kernel signature: b82f704ca56da9f9c3328a503bc184df5e683c87ccf37605d0a7434380377baa
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out
testing current HEAD 3fc898571b974f9a05e4e5c1fe17b18548207091
testing commit 3fc898571b974f9a05e4e5c1fe17b18548207091 with gcc (GCC) 8.1.0
kernel signature: cfbb161144ee834ea43122c26e34f81c902107cbb517a47cd719df3dad1a621e
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out
revisions tested: 2, total time: 23m51.28937595s (build: 17m20.498920391s, test: 6m4.610063262s)
the crash still happens on HEAD
commit msg: Linux 4.19.128
crash: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_team: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_team: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_hsr: link becomes ready
BUG: unable to handle kernel NULL pointer dereference at 0000000000000002
PGD 9e81c067 P4D 9e81c067 PUD 94189067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 7438 Comm: syz-executor.4 Not tainted 4.19.128-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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:413
Code: b6 8b e1 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 aa 08 1f fe 8b
RSP: 0018:ffff8880965577c0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffffff8abd2190 RCX: 1ffffffff157a43a
RDX: 0000000000000001 RSI: 0000000000000002 RDI: ffffffff8abd21d0
RBP: ffff8880965577d0 R08: ffffed10148221d6 R09: ffffed10148221d5
R10: ffffed10148221d5 R11: ffff8880a4110eab R12: ffffffff8abd21e0
R13: ffffffff8abd2190 R14: ffffffff8abd7a80 R15: ffffffff8abd226c
FS:  00007f9832692700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000002 CR3: 00000000a83ed000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 serial_out drivers/tty/serial/8250/8250.h:116 [inline]
 serial8250_clear_fifos.part.6+0x35/0xb0 drivers/tty/serial/8250/8250_port.c:556
 serial8250_clear_fifos drivers/tty/serial/8250/8250_port.c:555 [inline]
 serial8250_do_startup+0x34c/0x1b10 drivers/tty/serial/8250/8250_port.c:2194
 serial8250_startup+0x3f/0x50 drivers/tty/serial/8250/8250_port.c:2410
 uart_port_startup drivers/tty/serial/serial_core.c:218 [inline]
 uart_startup.part.18+0x38f/0x840 drivers/tty/serial/serial_core.c:257
 uart_startup drivers/tty/serial/serial_core.c:254 [inline]
 uart_set_info drivers/tty/serial/serial_core.c:997 [inline]
 uart_set_info_user drivers/tty/serial/serial_core.c:1025 [inline]
 uart_ioctl+0x12c8/0x2be0 drivers/tty/serial/serial_core.c:1348
 tty_ioctl+0x452/0x1290 drivers/tty/tty_io.c:2669
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688
 ksys_ioctl+0x62/0x90 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a919
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f9832691c78 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: 00007f98326926d4
R13: 00000000004c5e04 R14: 00000000004dc270 R15: 00000000ffffffff
Modules linked in:
CR2: 0000000000000002
IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bond: link becomes ready
---[ end trace 96e9c116262b7aa2 ]---
IPv6: ADDRCONF(NETDEV_CHANGE): team0: link becomes ready
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:413
IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready
Code: b6 8b e1 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 aa 08 1f fe 8b
RSP: 0018:ffff8880965577c0 EFLAGS: 00010202
IPv6: ADDRCONF(NETDEV_UP): veth1_to_hsr: link is not ready
RAX: dffffc0000000000 RBX: ffffffff8abd2190 RCX: 1ffffffff157a43a
IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready
RDX: 0000000000000001 RSI: 0000000000000002 RDI: ffffffff8abd21d0
IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
RBP: ffff8880965577d0 R08: ffffed10148221d6 R09: ffffed10148221d5
IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready
R10: ffffed10148221d5 R11: ffff8880a4110eab R12: ffffffff8abd21e0
IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready
R13: ffffffff8abd2190 R14: ffffffff8abd7a80 R15: ffffffff8abd226c
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_team: link becomes ready
FS:  00007f9832692700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fabc262b028 CR3: 00000000a83ed000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400