bisecting fixing commit since fb683b5e3f53a73e761952735736180939a313df
building syzkaller on 4b83c8fbed7b9cea831be880ec8aa1098b465f25
testing commit fb683b5e3f53a73e761952735736180939a313df with gcc (GCC) 8.1.0
kernel signature: 227f9626f76ce367b673bb8549f2d445266799038c5d433a311716c204e063ef
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem_serial_out
testing current HEAD 6dd0e32665e591e9debe3edaf73c2f8135bf047e
testing commit 6dd0e32665e591e9debe3edaf73c2f8135bf047e with gcc (GCC) 8.1.0
kernel signature: 5bd2c1c7ab578e1eefd53670e89af17d5efe230a86b0701fbc40cd07520308e5
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem_serial_out
revisions tested: 2, total time: 26m3.325401433s (build: 18m19.330589818s, test: 6m39.577994322s)
the crash still happens on HEAD
commit msg: Linux 4.19.115
crash: BUG: unable to handle kernel NULL pointer dereference in mem_serial_out
IPv6: ADDRCONF(NETDEV_CHANGE): bridge0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): veth1_to_hsr: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready
BUG: unable to handle kernel NULL pointer dereference at 0000000000000003
IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready
PGD 9e1b4067 P4D 9e1b4067 PUD 9e1b5067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 7435 Comm: syz-executor.2 Not tainted 4.19.115-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+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 cb 6a 1f fe 8b 55
RSP: 0018:ffff8880932ef7e0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffffffff8abcf0d0 RCX: 1ffffffff1579e22
RDX: 00000000000000bf RSI: 0000000000000003 RDI: ffffffff8abcf110
RBP: ffff8880932ef7f0 R08: ffffed101482a1ce R09: ffffed101482a1cd
R10: ffffed101482a1cd R11: ffff8880a4150e6b R12: ffffffff8abcf220
R13: ffffffff8abcf0d0 R14: ffffffff8abcf120 R15: ffffffff8abcf1ac
FS:  00007ff679ea9700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000003 CR3: 000000009e1b3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 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.19+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+0x12db/0x2bf0 drivers/tty/serial/serial_core.c:1348
 tty_ioctl+0x452/0x1290 drivers/tty/tty_io.c:2669
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready
 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): veth1_to_bond: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: 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
IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
IPv6: ADDRCONF(NETDEV_UP): veth0_to_hsr: link is not ready
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
IPv6: ADDRCONF(NETDEV_UP): veth1_to_hsr: link is not ready
RIP: 0033:0x45a6f9
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:00007ff679ea8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a6f9
RDX: 0000000020000080 RSI: 000000000000541f RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff679ea96d4
R13: 00000000004c5c0b R14: 00000000004dbf70 R15: 00000000ffffffff
Modules linked in:
hsr0: Slave A (hsr_slave_0) is not up; please bring it up to get a fully working HSR network
CR2: 0000000000000003
hsr0: Slave B (hsr_slave_1) is not up; please bring it up to get a fully working HSR network
---[ end trace 97e1bb32cde2c26e ]---
IPv6: ADDRCONF(NETDEV_UP): hsr0: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_hsr: 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): hsr_slave_1: 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 cb 6a 1f fe 8b 55
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bridge: link becomes ready
RSP: 0018:ffff8880932ef7e0 EFLAGS: 00010206
IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_0: link becomes ready
RAX: dffffc0000000000 RBX: ffffffff8abcf0d0 RCX: 1ffffffff1579e22
bridge0: port 1(bridge_slave_0) entered blocking state
RDX: 00000000000000bf RSI: 0000000000000003 RDI: ffffffff8abcf110
bridge0: port 1(bridge_slave_0) entered forwarding state
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_team: link becomes ready
RBP: ffff8880932ef7f0 R08: ffffed101482a1ce R09: ffffed101482a1cd
IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_0: link becomes ready
R10: ffffed101482a1cd R11: ffff8880a4150e6b R12: ffffffff8abcf220
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_team: link becomes ready
R13: ffffffff8abcf0d0 R14: ffffffff8abcf120 R15: ffffffff8abcf1ac
IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_1: link becomes ready
FS:  00007ff679ea9700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_1: link becomes ready
CR2: 0000565350419f69 CR3: 000000009e1b3000 CR4: 00000000001406e0
bridge0: port 2(bridge_slave_1) entered blocking state
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
bridge0: port 2(bridge_slave_1) entered forwarding state
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bond: link becomes ready
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bond: link becomes ready