bisecting fixing commit since 312017a460d5ea31d646e7148e400e13db799ddc
building syzkaller on 0ae38e44894e5a52fe35a56b1d2ad18477cc6b59
testing commit 312017a460d5ea31d646e7148e400e13db799ddc with gcc (GCC) 8.1.0
kernel signature: ee4f91434fdfbd2815ca84fc3b792e157a0cff6e03f5f5df884de4fcf4249b5c
all runs: crashed: BUG: unable to handle kernel paging request in insert_char
testing current HEAD 6dd0e32665e591e9debe3edaf73c2f8135bf047e
testing commit 6dd0e32665e591e9debe3edaf73c2f8135bf047e with gcc (GCC) 8.1.0
kernel signature: 098df1f671e32b93be981bb2f02c9f5da83aca75f26f836c404d328b6e9ac5fe
all runs: crashed: BUG: unable to handle kernel paging request in insert_char
revisions tested: 2, total time: 25m51.684661071s (build: 18m38.392675538s, test: 6m9.547357719s)
the crash still happens on HEAD
commit msg: Linux 4.19.115
crash: BUG: unable to handle kernel paging request in insert_char
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready
8021q: adding VLAN 0 to HW filter on device batadv0
BUG: unable to handle kernel paging request at 000000010000000e
PGD 91b89067 P4D 91b89067 PUD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 7604 Comm: syz-executor.1 Not tainted 4.19.115-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:memset16 arch/x86/include/asm/string_64.h:43 [inline]
RIP: 0010:scr_memsetw include/linux/vt_buffer.h:36 [inline]
RIP: 0010:insert_char+0x21d/0x440 drivers/tty/vt/vt.c:840
Code: 48 89 fa 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 01 0f 8e 21 01 00 00 44 89 f9 0f b7 83 c8 03 00 00 4c 89 e7 81 e1 ff ff ff 7f <f3> 66 ab 48 8d bb 78 04 00 00 48 b8 00 00 00 00 00 fc ff df 48 89
RSP: 0018:ffff88808ed9f708 EFLAGS: 00010202
RAX: 0000000000000720 RBX: ffff8880915955c0 RCX: 0000000000000001
RDX: 1ffff110122b2b31 RSI: 000000010000000e RDI: 000000010000000e
RBP: ffff88808ed9f758 R08: 0000000000000001 R09: ffff8880915955c0
R10: ffffed1015d44732 R11: 0000000000000040 R12: 000000010000000e
R13: ffff88809159594c R14: ffff8880915958f4 R15: 0000000000000001
FS:  00007fcdd27c8700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000010000000e CR3: 00000000902c0000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 csi_at drivers/tty/vt/vt.c:1989 [inline]
 do_con_trol+0x33e0/0x6370 drivers/tty/vt/vt.c:2436
 do_con_write.part.26+0xad0/0x1aa0 drivers/tty/vt/vt.c:2797
 do_con_write drivers/tty/vt/vt.c:2565 [inline]
 con_write+0x1f/0x80 drivers/tty/vt/vt.c:3132
 process_output_block drivers/tty/n_tty.c:593 [inline]
 n_tty_write+0x4a4/0x1060 drivers/tty/n_tty.c:2331
 do_tty_write drivers/tty/tty_io.c:960 [inline]
 tty_write+0x346/0x770 drivers/tty/tty_io.c:1044
 __vfs_write+0xe3/0x890 fs/read_write.c:485
 vfs_write+0x150/0x4d0 fs/read_write.c:549
 ksys_write+0x103/0x260 fs/read_write.c:599
 __do_sys_write fs/read_write.c:611 [inline]
 __se_sys_write fs/read_write.c:608 [inline]
 __x64_sys_write+0x6e/0xb0 fs/read_write.c:608
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a909
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:00007fcdd27c7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a909
RDX: 0000000000000078 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fcdd27c86d4
R13: 00000000004cbdc5 R14: 00000000004e5a58 R15: 00000000ffffffff
Modules linked in:
CR2: 000000010000000e
---[ end trace 7070cd17f56b19f9 ]---
RIP: 0010:memset16 arch/x86/include/asm/string_64.h:43 [inline]
RIP: 0010:scr_memsetw include/linux/vt_buffer.h:36 [inline]
RIP: 0010:insert_char+0x21d/0x440 drivers/tty/vt/vt.c:840
Code: 48 89 fa 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 01 0f 8e 21 01 00 00 44 89 f9 0f b7 83 c8 03 00 00 4c 89 e7 81 e1 ff ff ff 7f <f3> 66 ab 48 8d bb 78 04 00 00 48 b8 00 00 00 00 00 fc ff df 48 89
RSP: 0018:ffff88808ed9f708 EFLAGS: 00010202
RAX: 0000000000000720 RBX: ffff8880915955c0 RCX: 0000000000000001
RDX: 1ffff110122b2b31 RSI: 000000010000000e RDI: 000000010000000e
RBP: ffff88808ed9f758 R08: 0000000000000001 R09: ffff8880915955c0
R10: ffffed1015d44732 R11: 0000000000000040 R12: 000000010000000e
R13: ffff88809159594c R14: ffff8880915958f4 R15: 0000000000000001
FS:  00007fcdd27c8700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000010000000e CR3: 00000000902c0000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400