bisecting fixing commit since b0cdffaa546e24acf92ab3b0d4e917a51aff6a82
building syzkaller on 4de4e9f01d7139b72102ae0b8a1e810730467774
testing commit b0cdffaa546e24acf92ab3b0d4e917a51aff6a82 with gcc (GCC) 8.1.0
kernel signature: 15ad7070144f877fec6563fb05c973aa4c83327ba3b0bf166b394a986d489865
all runs: crashed: KASAN: null-ptr-deref Read in insert_char
testing current HEAD d71f695ce745df9544a85d8a762f16d72e72df00
testing commit d71f695ce745df9544a85d8a762f16d72e72df00 with gcc (GCC) 8.1.0
kernel signature: c00b6aa84a68b798c8abb7bb10bd5710c85faaca9f9e0af8e3bf69d7d273d6d8
all runs: crashed: KASAN: null-ptr-deref Read in insert_char
revisions tested: 2, total time: 25m37.311798165s (build: 17m46.148460166s, test: 6m18.205570201s)
the crash still happens on HEAD
commit msg: Linux 4.14.179
crash: KASAN: null-ptr-deref Read in insert_char
device veth0_vlan entered promiscuous mode
device veth1_vlan entered promiscuous mode
IPv6: ADDRCONF(NETDEV_UP): macvlan0: link is not ready
IPv6: ADDRCONF(NETDEV_UP): macvlan1: link is not ready
==================================================================
BUG: KASAN: null-ptr-deref in memmove include/linux/string.h:362 [inline]
BUG: KASAN: null-ptr-deref in scr_memmovew include/linux/vt_buffer.h:68 [inline]
BUG: KASAN: null-ptr-deref in insert_char+0xc3/0x280 drivers/tty/vt/vt.c:534
Read of size 4294967294 at addr 0000000000000010 by task syz-executor.4/7655

CPU: 0 PID: 7655 Comm: syz-executor.4 Not tainted 4.14.179-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:1640 [inline]
 do_con_trol+0x1f3c/0x61a0 drivers/tty/vt/vt.c:2087
 do_con_write.part.22+0x9bc/0x19c0 drivers/tty/vt/vt.c:2447
 do_con_write drivers/tty/vt/vt.c:2218 [inline]
 con_write+0x1f/0x80 drivers/tty/vt/vt.c:2798
 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: 0033:0x45af49
RSP: 002b:00007f08351b8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045af49
RDX: 0000000000000078 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f08351b96d4
R13: 00000000004cce66 R14: 00000000004e82a0 R15: 00000000ffffffff
==================================================================