bisecting fixing commit since fb683b5e3f53a73e761952735736180939a313df
building syzkaller on 1508f45368a309a3b1196a342b3d64ce7be4cc43
testing commit fb683b5e3f53a73e761952735736180939a313df with gcc (GCC) 8.1.0
kernel signature: c035f4a56747dce8b63f055b03d464141ebabbb72de8c7185f61a7cef809e074
all runs: crashed: KASAN: global-out-of-bounds Read in fb_pad_aligned_buffer
testing current HEAD 10ad6cfd57360760116cde00a8ef756e121367a9
testing commit 10ad6cfd57360760116cde00a8ef756e121367a9 with gcc (GCC) 8.1.0
kernel signature: a8b949f936898705491d32d97c0c4f94784b5de6d8d6d117081516ab2cf37836
all runs: crashed: KASAN: global-out-of-bounds Read in fb_pad_aligned_buffer
revisions tested: 2, total time: 24m46.184166881s (build: 17m45.213570183s, test: 6m3.212268667s)
the crash still happens on HEAD
commit msg: Linux 4.19.148
crash: KASAN: global-out-of-bounds Read in fb_pad_aligned_buffer
IPv6: ADDRCONF(NETDEV_UP): vxcan1: 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 __fb_pad_aligned_buffer include/linux/fb.h:674 [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 ffffffff876958f6 by task syz-executor.3/7439

CPU: 1 PID: 7439 Comm: syz-executor.3 Not tainted 4.19.148-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
 print_address_description.cold.8+0x58/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
 __fb_pad_aligned_buffer include/linux/fb.h:674 [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+0x7b9/0xde0 drivers/video/fbdev/core/bitblit.c:185
 fbcon_putcs+0x2fb/0x5a0 drivers/video/fbdev/core/fbcon.c:1269
 do_update_region+0x30c/0x640 drivers/tty/vt/vt.c:683
 redraw_screen+0x515/0x820 drivers/tty/vt/vt.c:1031
 fbcon_do_set_font+0x5c3/0x890 drivers/video/fbdev/core/fbcon.c:2409
 fbcon_copy_font+0x116/0x1a0 drivers/video/fbdev/core/fbcon.c:2424
 con_font_copy drivers/tty/vt/vt.c:4593 [inline]
 con_font_op+0x228/0x11f0 drivers/tty/vt/vt.c:4608
 vt_ioctl+0xa4e/0x23f0 drivers/tty/vt/vt_ioctl.c:990
 tty_ioctl+0x452/0x1290 drivers/tty/tty_io.c:2669
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688
 ksys_ioctl+0x62/0x90 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a779
Code: 2d 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 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f77ca97ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a779
RDX: 0000000020000000 RSI: 0000000000004b72 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f77ca97f6d4
R13: 00000000004c38ab R14: 00000000004d8df8 R15: 00000000ffffffff

The buggy address belongs to the variable:
 oid_index+0x76/0xa60

Memory state around the buggy address:
 ffffffff87695780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff87695800: 00 00 00 00 00 00 00 00 00 00 00 05 fa fa fa fa
>ffffffff87695880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 06 fa
                                                             ^
 ffffffff87695900: fa fa fa fa 00 02 fa fa fa fa fa fa 00 01 fa fa
 ffffffff87695980: fa fa fa fa 00 00 02 fa fa fa fa fa 00 03 fa fa
==================================================================