bisecting fixing commit since fb683b5e3f53a73e761952735736180939a313df
building syzkaller on 4b83c8fbed7b9cea831be880ec8aa1098b465f25
testing commit fb683b5e3f53a73e761952735736180939a313df with gcc (GCC) 8.1.0
kernel signature: 202b6c7510a75ebc9a06c7552352cc1ea4c2cc89efabce3511a924d8e86e63d0
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem_serial_out
testing current HEAD c14d30dc9987047b439b03d6e6db7d54d9f7f180
testing commit c14d30dc9987047b439b03d6e6db7d54d9f7f180 with gcc (GCC) 8.1.0
kernel signature: 3b02de3961486faeddcfc908fcb371ee7656fb638f241660e8dbc99f0b16fdd0
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem_serial_out
revisions tested: 2, total time: 26m56.318042189s (build: 19m16.681620199s, test: 6m22.309348644s)
the crash still happens on HEAD
commit msg: Linux 4.19.139
crash: BUG: unable to handle kernel NULL pointer dereference in mem_serial_out
IPv6: ADDRCONF(NETDEV_CHANGE): bridge0: link becomes ready
8021q: adding VLAN 0 to HW filter on device batadv0
IPv6: ADDRCONF(NETDEV_UP): veth1_to_hsr: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready
BUG: unable to handle kernel NULL pointer dereference at 0000000000000003
IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready
PGD 93bff067 P4D 93bff067 PUD 95d54067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 7442 Comm: syz-executor.3 Not tainted 4.19.139-syzkaller #0
IPv6: ADDRCONF(NETDEV_UP): veth0_to_hsr: link is not ready
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+0x61/0x90 drivers/tty/serial/8250/8250_port.c:407
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 23 48 63 f6 48 03 73 40 <88> 16 48 83 c4 08 5b 5d c3 89 55 f0 89 75 f4 e8 3b 01 1d fe 8b 55
RSP: 0018:ffff88809643f7e0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffffffff8abda150 RCX: 1ffffffff157b432
RDX: 00000000000000bf RSI: 0000000000000003 RDI: ffffffff8abda190
RBP: ffff88809643f7f0 R08: ffffed101481c1ce R09: ffffed101481c1cd
R10: ffffed101481c1cd R11: ffff8880a40e0e6b R12: ffffffff8abda2a0
R13: ffffffff8abda150 R14: ffffffff8abda1a0 R15: ffffffff8abda22c
FS:  00007fb61def1700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000003 CR3: 0000000093bfe000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
IPv6: ADDRCONF(NETDEV_UP): veth1_to_hsr: link is not ready
 serial_port_out include/linux/serial_core.h:274 [inline]
 serial8250_do_startup+0xd7f/0x1b10 drivers/tty/serial/8250/8250_port.c:2136
 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
hsr0: Slave A (hsr_slave_0) is not up; please bring it up to get a fully working HSR network
 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
hsr0: Slave B (hsr_slave_1) is not up; please bring it up to get a fully working HSR network
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688
IPv6: ADDRCONF(NETDEV_UP): hsr0: link is not ready
IPv6: ADDRCONF(NETDEV_UP): vxcan0: link is not ready
 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
IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a779
Code: 2d 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 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00
8021q: adding VLAN 0 to HW filter on device batadv0
RSP: 002b:00007fb61def0c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a779
RDX: 0000000020000080 RSI: 000000000000541f RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb61def16d4
R13: 00000000004c5c8b R14: 00000000004dbff0 R15: 00000000ffffffff
Modules linked in:
CR2: 0000000000000003
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_hsr: link becomes ready
---[ end trace e3b22380718a95be ]---
IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_1: link becomes ready
RIP: 0010:writeb arch/x86/include/asm/io.h:65 [inline]
RIP: 0010:mem_serial_out+0x61/0x90 drivers/tty/serial/8250/8250_port.c:407
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes 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 23 48 63 f6 48 03 73 40 <88> 16 48 83 c4 08 5b 5d c3 89 55 f0 89 75 f4 e8 3b 01 1d fe 8b 55
IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_1: link becomes ready
RSP: 0018:ffff88809643f7e0 EFLAGS: 00010206
bridge0: port 2(bridge_slave_1) entered blocking state
RAX: dffffc0000000000 RBX: ffffffff8abda150 RCX: 1ffffffff157b432
bridge0: port 2(bridge_slave_1) entered forwarding state
RDX: 00000000000000bf RSI: 0000000000000003 RDI: ffffffff8abda190
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bond: link becomes ready
RBP: ffff88809643f7f0 R08: ffffed101481c1ce R09: ffffed101481c1cd
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_team: link becomes ready
R10: ffffed101481c1cd R11: ffff8880a40e0e6b R12: ffffffff8abda2a0
IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_1: link becomes ready
R13: ffffffff8abda150 R14: ffffffff8abda1a0 R15: ffffffff8abda22c
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_hsr: link becomes ready
FS:  00007fb61def1700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_0: link becomes ready
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_hsr: link becomes ready
CR2: 00007f89807a2000 CR3: 0000000093bfe000 CR4: 00000000001406e0
IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_1: link becomes ready
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready