bisecting fixing commit since 5d30bcacd91af6874481129797af364a53cd9b46
building syzkaller on a8c6a3f8da30ccf825c6001c81a8adff21829c30
testing commit 5d30bcacd91af6874481129797af364a53cd9b46 with gcc (GCC) 8.1.0
kernel signature: 1ef3ecd6891411ee298d0a96d64528e561e3e2208846a847aabc83821e9bf203
all runs: crashed: KASAN: global-out-of-bounds Read in fb_pad_aligned_buffer
testing current HEAD 8c1684bb81f173543599f1848c29a2a3b1ee5907
testing commit 8c1684bb81f173543599f1848c29a2a3b1ee5907 with gcc (GCC) 8.1.0
kernel signature: 28666836796c791f841ada0e665e5a06c248067a87cf0d28f01ac0e04b6bd65e
all runs: crashed: KASAN: global-out-of-bounds Read in fb_pad_aligned_buffer
revisions tested: 2, total time: 20m48.13300393s (build: 12m39.65995426s, test: 7m15.802025804s)
the crash still happens on HEAD
commit msg: Merge tag 'for-linus-2020-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
crash: KASAN: global-out-of-bounds Read in fb_pad_aligned_buffer
==================================================================
BUG: KASAN: global-out-of-bounds in __fb_pad_aligned_buffer include/linux/fb.h:655 [inline]
BUG: KASAN: global-out-of-bounds in fb_pad_aligned_buffer+0xd3/0x130 drivers/video/fbdev/core/fbmem.c:116
Read of size 1 at addr ffffffff87d128e0 by task syz-executor.0/8441

CPU: 1 PID: 8441 Comm: syz-executor.0 Not tainted 5.7.0-rc5-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+0x128/0x182 lib/dump_stack.c:118
 print_address_description.constprop.8.cold.10+0x56/0x317 mm/kasan/report.c:382
 __kasan_report.cold.11+0x35/0x4d mm/kasan/report.c:511
 kasan_report+0x32/0x50 mm/kasan/common.c:625
 __fb_pad_aligned_buffer include/linux/fb.h:655 [inline]
 fb_pad_aligned_buffer+0xd3/0x130 drivers/video/fbdev/core/fbmem.c:116
 bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:99 [inline]
 bit_putcs+0x70d/0xba0 drivers/video/fbdev/core/bitblit.c:185
 fbcon_putcs+0x307/0x500 drivers/video/fbdev/core/fbcon.c:1362
 do_update_region+0x2d8/0x5b0 drivers/tty/vt/vt.c:683
 redraw_screen+0x53c/0x6c0 drivers/tty/vt/vt.c:1029
 fbcon_do_set_font+0x633/0x9b0 drivers/video/fbdev/core/fbcon.c:2614
 con_font_copy drivers/tty/vt/vt.c:4627 [inline]
 con_font_op+0x214/0xf90 drivers/tty/vt/vt.c:4642
 vt_ioctl+0xa39/0x2330 drivers/tty/vt/vt_ioctl.c:980
 tty_ioctl+0x461/0x1220 drivers/tty/tty_io.c:2656
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0xb8/0x110 fs/ioctl.c:771
 __do_sys_ioctl fs/ioctl.c:780 [inline]
 __se_sys_ioctl fs/ioctl.c:778 [inline]
 __x64_sys_ioctl+0x6a/0xb0 fs/ioctl.c:778
 do_syscall_64+0xc6/0x620 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45c889
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:00007fbfbd1adc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fbfbd1ae6d4 RCX: 000000000045c889
RDX: 0000000020000080 RSI: 0000000000004b72 RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000036c R14: 00000000004c5e17 R15: 000000000076bf0c

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

Memory state around the buggy address:
 ffffffff87d12780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff87d12800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffff87d12880: 00 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa
                                                       ^
 ffffffff87d12900: 06 fa fa fa fa fa fa fa 05 fa fa fa fa fa fa fa
 ffffffff87d12980: 06 fa fa fa fa fa fa fa 00 00 03 fa fa fa fa fa
==================================================================