bisecting fixing commit since 357668399cf70ccdc0ee8967bff3448d0f4f9ae1
building syzkaller on 5d7b90f1af2e3bf33992b75e7fcf0bab6bf49bd6
testing commit 357668399cf70ccdc0ee8967bff3448d0f4f9ae1 with gcc (GCC) 8.1.0
kernel signature: 72cfae7d5b868a4abee34406832259125f9d0ab3a4a3fc93bd12e04be279a3e5
all runs: crashed: KASAN: null-ptr-deref Read in do_con_trol
testing current HEAD 3fc898571b974f9a05e4e5c1fe17b18548207091
testing commit 3fc898571b974f9a05e4e5c1fe17b18548207091 with gcc (GCC) 8.1.0
kernel signature: f7b704c2cb716f25f7e3294dc8cfb4b29c143a53703ea1fb7a7cc692015868db
all runs: crashed: KASAN: null-ptr-deref Read in do_con_trol
revisions tested: 2, total time: 24m35.695240748s (build: 17m36.209849858s, test: 6m7.256238425s)
the crash still happens on HEAD
commit msg: Linux 4.19.128
crash: KASAN: null-ptr-deref Read in do_con_trol
batman_adv: batadv0: Interface activated: batadv_slave_1
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
==================================================================
BUG: KASAN: null-ptr-deref in memcpy include/linux/string.h:348 [inline]
BUG: KASAN: null-ptr-deref in scr_memcpyw include/linux/vt_buffer.h:49 [inline]
BUG: KASAN: null-ptr-deref in delete_char drivers/tty/vt/vt.c:858 [inline]
BUG: KASAN: null-ptr-deref in csi_P drivers/tty/vt/vt.c:2016 [inline]
BUG: KASAN: null-ptr-deref in do_con_trol+0x2c1a/0x6360 drivers/tty/vt/vt.c:2390
Read of size 4294967294 at addr 0000000000000012 by task syz-executor.0/8066

CPU: 1 PID: 8066 Comm: syz-executor.0 Not tainted 4.19.128-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x123/0x177 lib/dump_stack.c:118
 kasan_report_error mm/kasan/report.c:352 [inline]
 kasan_report.cold.9+0x6d/0x309 mm/kasan/report.c:412
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
 memcpy+0x23/0x50 mm/kasan/kasan.c:302
 memcpy include/linux/string.h:348 [inline]
 scr_memcpyw include/linux/vt_buffer.h:49 [inline]
 delete_char drivers/tty/vt/vt.c:858 [inline]
 csi_P drivers/tty/vt/vt.c:2016 [inline]
 do_con_trol+0x2c1a/0x6360 drivers/tty/vt/vt.c:2390
 do_con_write.part.21+0xad0/0x1aa0 drivers/tty/vt/vt.c:2803
 do_con_write drivers/tty/vt/vt.c:2571 [inline]
 con_write+0x1f/0x80 drivers/tty/vt/vt.c:3138
 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: 0033:0x45c6c9
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:00007f6180692c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f61806936d4 RCX: 000000000045c6c9
RDX: 0000000000000078 RSI: 0000000020000140 RDI: 0000000000000004
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000ca8 R14: 00000000004ceba3 R15: 000000000076bf2c
==================================================================