bisecting fixing commit since c196b3a9c83ae3491280b739d231d02b3cb9d041
building syzkaller on 51a9082e064119316893e12187cab2843283ed4d
testing commit c196b3a9c83ae3491280b739d231d02b3cb9d041 with gcc (GCC) 8.4.1 20210217
kernel signature: 34c60180f3abc11a4fe122f4892e5d3ef4fd2ef0709f6c24cb08d1e670b6bbf4
all runs: crashed: KASAN: global-out-of-bounds Read in soft_cursor
testing current HEAD cf256fbcbe347b7d0ff58fe2dfa382a156bd3694
testing commit cf256fbcbe347b7d0ff58fe2dfa382a156bd3694 with gcc (GCC) 8.4.1 20210217
kernel signature: d64265b5a484329d31928fa3a9d5c2075aff58bab5ba95c18f9b28737449c492
all runs: crashed: KASAN: global-out-of-bounds Read in soft_cursor
revisions tested: 2, total time: 29m23.469189416s (build: 22m21.966908176s, test: 6m29.062089194s)
the crash still happens on HEAD
commit msg: Linux 4.14.231
crash: KASAN: global-out-of-bounds Read in soft_cursor
IPv6: ADDRCONF(NETDEV_UP): macvlan0: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth1_to_batadv: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth0_macvtap: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth1_macvtap: link is not ready
==================================================================
BUG: KASAN: global-out-of-bounds in memcpy include/linux/string.h:376 [inline]
BUG: KASAN: global-out-of-bounds in soft_cursor+0x430/0xc70 drivers/video/fbdev/core/softcursor.c:70
Read of size 32 at addr ffffffff87cf0010 by task syz-executor.2/9663

CPU: 0 PID: 9663 Comm: syz-executor.2 Not tainted 4.14.231-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+0x14b/0x1e7 lib/dump_stack.c:58
 print_address_description.cold.6+0x114/0x1ca mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold.7+0x11a/0x2d3 mm/kasan/report.c:393
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13c/0x1b0 mm/kasan/kasan.c:267
 memcpy+0x23/0x50 mm/kasan/kasan.c:302
 memcpy include/linux/string.h:376 [inline]
 soft_cursor+0x430/0xc70 drivers/video/fbdev/core/softcursor.c:70
 bit_cursor+0xd71/0x1aa0 drivers/video/fbdev/core/bitblit.c:377
 fbcon_cursor+0x45b/0x660 drivers/video/fbdev/core/fbcon.c:1290
 hide_cursor+0x73/0x2b0 drivers/tty/vt/vt.c:590
 update_region drivers/tty/vt/vt.c:390 [inline]
 update_region+0xb8/0x100 drivers/tty/vt/vt.c:385
 vcs_write+0x2cc/0xae0 drivers/tty/vt/vc_screen.c:549
 __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+0x46/0xbb
RIP: 0033:0x4659b9
RSP: 002b:00007fab8e959188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000055bf40 RCX: 00000000004659b9
RDX: 0000000000000121 RSI: 00000000200000c0 RDI: 0000000000000004
RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf40
R13: 00007ffd76f02e7f R14: 00007fab8e959300 R15: 0000000000022000

The buggy address belongs to the variable:
 oid_index+0x850/0x9a0

Memory state around the buggy address:
 ffffffff87ceff00: fa fa fa fa 05 fa fa fa fa fa fa fa 01 fa fa fa
 ffffffff87ceff80: fa fa fa fa 00 00 02 fa fa fa fa fa 00 00 00 fa
>ffffffff87cf0000: fa fa fa fa 00 00 00 00 00 01 fa fa fa fa fa fa
                         ^
 ffffffff87cf0080: 00 00 00 00 01 fa fa fa fa fa fa fa 00 00 00 05
 ffffffff87cf0100: fa fa fa fa 00 00 00 00 fa fa fa fa 00 03 fa fa
==================================================================