bisecting fixing commit since a844dc4c544291470aa69edbe2434b040794e269
building syzkaller on 1508f45368a309a3b1196a342b3d64ce7be4cc43
testing commit a844dc4c544291470aa69edbe2434b040794e269 with gcc (GCC) 8.1.0
kernel signature: ccdb04221c9f422dda1eb67c0cd7c3b1e9f906913ed7ba66fc36b18a084fded9
all runs: crashed: KASAN: global-out-of-bounds Read in fb_pad_aligned_buffer
testing current HEAD e0f8b8a65a473a8baa439cf865a694bbeb83fe90
testing commit e0f8b8a65a473a8baa439cf865a694bbeb83fe90 with gcc (GCC) 8.1.0
kernel signature: c61ef21ccefcba163bc727ac8a6127262b0ec7019c1fec31855976b216f8ffac
all runs: crashed: KASAN: global-out-of-bounds Read in fb_pad_aligned_buffer
revisions tested: 2, total time: 24m59.714929819s (build: 17m53.517875115s, test: 6m27.951389841s)
the crash still happens on HEAD
commit msg: Linux 4.14.170
crash: KASAN: global-out-of-bounds Read in fb_pad_aligned_buffer
IPv6: ADDRCONF(NETDEV_UP): bridge_slave_1: link is not ready
IPv6: ADDRCONF(NETDEV_UP): team0: link is not ready
8021q: adding VLAN 0 to HW filter on device team0
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready
==================================================================
BUG: KASAN: global-out-of-bounds in __fb_pad_aligned_buffer include/linux/fb.h:663 [inline]
BUG: KASAN: global-out-of-bounds in fb_pad_aligned_buffer+0xd3/0x130 drivers/video/fbdev/core/fbmem.c:122
Read of size 1 at addr ffffffff87060736 by task syz-executor.0/7237

CPU: 0 PID: 7237 Comm: syz-executor.0 Not tainted 4.14.170-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
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427
 __fb_pad_aligned_buffer include/linux/fb.h:663 [inline]
 fb_pad_aligned_buffer+0xd3/0x130 drivers/video/fbdev/core/fbmem.c:122
 bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:99 [inline]
 bit_putcs+0x7fd/0xee0 drivers/video/fbdev/core/bitblit.c:185
 fbcon_putcs+0x2fb/0x5b0 drivers/video/fbdev/core/fbcon.c:1298
 do_update_region+0x304/0x630 drivers/tty/vt/vt.c:373
 redraw_screen+0x50d/0x7f0 drivers/tty/vt/vt.c:704
 fbcon_do_set_font+0x656/0xa20 drivers/video/fbdev/core/fbcon.c:2561
 fbcon_copy_font+0x116/0x1a0 drivers/video/fbdev/core/fbcon.c:2576
 con_font_copy drivers/tty/vt/vt.c:4218 [inline]
 con_font_op+0x219/0x1020 drivers/tty/vt/vt.c:4233
 vt_ioctl+0x9d7/0x21d0 drivers/tty/vt/vt_ioctl.c:979
 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: 0033:0x45a6f9
RSP: 002b:00007febd7cb6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a6f9
RDX: 0000000020000000 RSI: 0000000000004b72 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007febd7cb76d4
R13: 00000000004c382b R14: 00000000004d8d78 R15: 00000000ffffffff

The buggy address belongs to the variable:
 oid_index+0x76/0x9a0

Memory state around the buggy address:
 ffffffff87060600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff87060680: 00 00 00 05 fa fa fa fa 00 00 00 00 00 00 00 00
>ffffffff87060700: 00 00 00 00 00 00 06 fa fa fa fa fa 00 02 fa fa
                                     ^
 ffffffff87060780: fa fa fa fa 00 01 fa fa fa fa fa fa 00 00 02 fa
 ffffffff87060800: fa fa fa fa 00 03 fa fa fa fa fa fa 07 fa fa fa
==================================================================