bisecting fixing commit since 7d120bf21c05cbe30a679f0feeca884eeaceb069 building syzkaller on 79b211f74b08737aeb4934c6ff69a263b3c38013 testing commit 7d120bf21c05cbe30a679f0feeca884eeaceb069 with gcc (GCC) 8.1.0 kernel signature: 7623c5ed061a1aa9c2ee95d258cbedf2044503e09f69245e7cb05d13f96ac6cb all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out testing current HEAD 9b15f7fae677336e04b9e026ff91854e43165455 testing commit 9b15f7fae677336e04b9e026ff91854e43165455 with gcc (GCC) 8.1.0 kernel signature: 3e6da2c587e45d08ed77f2ce425cde2b0cfe7fce839c5cc1a4e0795c43ddd42e all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out revisions tested: 2, total time: 25m23.58408466s (build: 18m9.256927724s, test: 6m43.141869572s) the crash still happens on HEAD commit msg: Linux 4.19.104 crash: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out IPv6: ADDRCONF(NETDEV_CHANGE): team0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_hsr: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): hsr_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 BUG: unable to handle kernel NULL pointer dereference at 0000000000000002 IPv6: ADDRCONF(NETDEV_UP): veth0_to_hsr: link is not ready PGD 9e7cf067 P4D 9e7cf067 PUD 80fb7067 PMD 0 IPv6: ADDRCONF(NETDEV_UP): veth1_to_hsr: link is not ready Oops: 0002 [#1] PREEMPT SMP KASAN hsr0: Slave B (hsr_slave_1) is not up; please bring it up to get a fully working HSR network CPU: 0 PID: 7252 Comm: syz-executor.2 Not tainted 4.19.104-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 0e 20 fe 8b RSP: 0018:ffff888074bbf7c0 EFLAGS: 00010202 IPv6: ADDRCONF(NETDEV_UP): hsr0: link is not ready RAX: dffffc0000000000 RBX: ffffffff8abcd0d0 RCX: 1ffffffff1579a22 IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready RDX: 0000000000000001 RSI: 0000000000000002 RDI: ffffffff8abcd110 RBP: ffff888074bbf7d0 R08: ffffed10432741ce R09: ffffed10432741cd R10: ffffed10432741cd R11: ffff8882193a0e6b R12: ffffffff8abcd120 R13: ffffffff8abcd0d0 R14: ffffffff8abd29c0 R15: ffffffff8abcd1ac FS: 00007fb9763c2700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000002 CR3: 000000009b70d000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: IPv6: ADDRCONF(NETDEV_UP): vxcan0: link is not ready 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 IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready serial8250_clear_fifos drivers/tty/serial/8250/8250_port.c:555 [inline] serial8250_do_startup+0x34c/0x1ad0 drivers/tty/serial/8250/8250_port.c:2194 serial8250_startup+0x3f/0x50 drivers/tty/serial/8250/8250_port.c:2406 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 8021q: adding VLAN 0 to HW filter on device batadv0 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:00007fb9763c1c78 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: 00007fb9763c26d4 R13: 00000000004c5e04 R14: 00000000004dc270 R15: 00000000ffffffff Modules linked in: CR2: 0000000000000002 IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready ---[ end trace aa69c238fc4b416e ]--- 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_CHANGE): veth0_to_hsr: 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 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 0e 20 fe 8b IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_0: link becomes ready RSP: 0018:ffff888074bbf7c0 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: ffffffff8abcd0d0 RCX: 1ffffffff1579a22 RDX: 0000000000000001 RSI: 0000000000000002 RDI: ffffffff8abcd110 RBP: ffff888074bbf7d0 R08: ffffed10432741ce R09: ffffed10432741cd R10: ffffed10432741cd R11: ffff8882193a0e6b R12: ffffffff8abcd120 R13: ffffffff8abcd0d0 R14: ffffffff8abd29c0 R15: ffffffff8abcd1ac FS: 00007fb9763c2700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000002 CR3: 000000009b70d000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400