bisecting fixing commit since 4c5bf01e16a7ec59e59a38a61f793c5d1d5560c7
building syzkaller on 25a0186eba20ef6f4f657039ff02eff52a838b1c
testing commit 4c5bf01e16a7ec59e59a38a61f793c5d1d5560c7 with gcc (GCC) 8.1.0
kernel signature: 7e36d9f3e0b9b991f70e29b26aa2b7683784cdb6a43ef6d73e53d92ea961a192
all runs: crashed: KASAN: global-out-of-bounds Read in fbcon_get_font
testing current HEAD 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796
testing commit 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796 with gcc (GCC) 8.1.0
kernel signature: 4754fea668a032a16eb574267457ebc474d0161e50b9aced57004a0b82f7fb59
all runs: crashed: KASAN: global-out-of-bounds Read in fbcon_get_font
revisions tested: 2, total time: 24m29.177156376s (build: 16m57.302363061s, test: 6m33.061295361s)
the crash still happens on HEAD
commit msg: Linux 4.14.171
crash: KASAN: global-out-of-bounds Read in fbcon_get_font
IPv6: ADDRCONF(NETDEV_UP): hsr0: link is not ready
IPv6: ADDRCONF(NETDEV_UP): vxcan0: link is not ready
IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
IPv6: ADDRCONF(NETDEV_UP): vxcan0: link is not ready
==================================================================
BUG: KASAN: global-out-of-bounds in memcpy include/linux/string.h:347 [inline]
BUG: KASAN: global-out-of-bounds in fbcon_get_font+0x21c/0x570 drivers/video/fbdev/core/fbcon.c:2421
Read of size 32 at addr ffffffff870601e0 by task syz-executor.3/7181

CPU: 0 PID: 7181 Comm: syz-executor.3 Not tainted 4.14.171-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
 print_address_description.cold.7+0x135/0x1c9 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report.cold.8+0x11a/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
 memcpy+0x23/0x50 mm/kasan/kasan.c:302
 memcpy include/linux/string.h:347 [inline]
 fbcon_get_font+0x21c/0x570 drivers/video/fbdev/core/fbcon.c:2421
 con_font_get drivers/tty/vt/vt.c:4078 [inline]
 con_font_op+0x75c/0x1020 drivers/tty/vt/vt.c:4229
 do_fontx_ioctl drivers/tty/vt/vt_ioctl.c:244 [inline]
 vt_ioctl+0xd52/0x21d0 drivers/tty/vt/vt_ioctl.c:944
 tty_ioctl+0x434/0x1260 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x74/0x80 fs/ioctl.c:692
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45a9e9
RSP: 002b:00007f441d80fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a9e9
RDX: 0000000020000200 RSI: 0000000000004b60 RDI: 0000000000000004
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f441d8106d4
R13: 00000000004c5bc8 R14: 00000000004dc1f0 R15: 00000000ffffffff

The buggy address belongs to the variable:
 fontdata_8x16+0x1000/0x1120

Memory state around the buggy address:
 ffffffff87060080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff87060100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffff87060180: 00 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa
                                                       ^
 ffffffff87060200: 06 fa fa fa fa fa fa fa 05 fa fa fa fa fa fa fa
 ffffffff87060280: 06 fa fa fa fa fa fa fa 00 00 03 fa fa fa fa fa
==================================================================