bisecting fixing commit since a844dc4c544291470aa69edbe2434b040794e269
building syzkaller on 4b83c8fbed7b9cea831be880ec8aa1098b465f25
testing commit a844dc4c544291470aa69edbe2434b040794e269 with gcc (GCC) 8.1.0
kernel signature: 9fd6eeb7fdf27b0cdadf2fcab8f3ed0f88f2d309f6808f76d065b519ce70d761
all runs: crashed: KASAN: user-memory-access Read in insert_char
testing current HEAD 78d697fc93f98054e36a3ab76dca1a88802ba7be
testing commit 78d697fc93f98054e36a3ab76dca1a88802ba7be with gcc (GCC) 8.1.0
kernel signature: 5f330d96d2ee4d3a2de21dc0bd42c386081934d0c0121bf1fc65e4291a35efd6
all runs: crashed: KASAN: user-memory-access Read in insert_char
revisions tested: 2, total time: 25m30.504198923s (build: 18m29.029038373s, test: 6m14.908020051s)
the crash still happens on HEAD
commit msg: Linux 4.14.172
crash: KASAN: user-memory-access Read 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
8021q: adding VLAN 0 to HW filter on device batadv0
==================================================================
BUG: KASAN: user-memory-access in memmove include/linux/string.h:362 [inline]
BUG: KASAN: user-memory-access in scr_memmovew include/linux/vt_buffer.h:68 [inline]
BUG: KASAN: user-memory-access in insert_char+0xc3/0x280 drivers/tty/vt/vt.c:534
Read of size 212 at addr 00000000ffffff3a by task syz-executor.0/7160

CPU: 1 PID: 7160 Comm: syz-executor.0 Not tainted 4.14.172-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xf7/0x13b lib/dump_stack.c:58
 kasan_report_error mm/kasan/report.c:349 [inline]
 kasan_report.cold.8+0x6d/0x2d3 mm/kasan/report.c:409
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
 memmove+0x23/0x50 mm/kasan/kasan.c:293
 memmove include/linux/string.h:362 [inline]
 scr_memmovew include/linux/vt_buffer.h:68 [inline]
 insert_char+0xc3/0x280 drivers/tty/vt/vt.c:534
 csi_at drivers/tty/vt/vt.c:1627 [inline]
 do_con_trol+0x1f3c/0x61a0 drivers/tty/vt/vt.c:2074
 do_con_write.part.22+0x9bc/0x19c0 drivers/tty/vt/vt.c:2434
 do_con_write drivers/tty/vt/vt.c:2205 [inline]
 con_write+0x1f/0x80 drivers/tty/vt/vt.c:2787
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0x498/0x1040 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:959 [inline]
 tty_write+0x346/0x770 drivers/tty/tty_io.c:1043
 __vfs_write+0xdb/0x840 fs/read_write.c:480
 vfs_write+0x150/0x4f0 fs/read_write.c:544
 SYSC_write fs/read_write.c:590 [inline]
 SyS_write+0x100/0x250 fs/read_write.c:582
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45a6f9
RSP: 002b:00007f86bb69cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a6f9
RDX: 0000000000000078 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f86bb69d6d4
R13: 00000000004cbbaf R14: 00000000004e5858 R15: 00000000ffffffff
==================================================================