[v6.1] KASAN: global-out-of-bounds Read in bit_putcs

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d7039b844a1c Linux 6.1.116
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11a834e8580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e70423a11a31a773
dashboard link: https://syzkaller.appspot.com/bug?extid=6ba31a6c6c0465238a6a
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3797d90cbed7/disk-d7039b84.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9726bc0bc28f/vmlinux-d7039b84.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0b4bbd21cac0/Image-d7039b84.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6ba31a...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: global-out-of-bounds in __fb_pad_aligned_buffer include/linux/fb.h:655 [inline]
BUG: KASAN: global-out-of-bounds in bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
BUG: KASAN: global-out-of-bounds in bit_putcs+0x9b8/0xe30 drivers/video/fbdev/core/bitblit.c:185
Read of size 1 at addr ffff8000128f7550 by task syz.5.545/6759

CPU: 1 PID: 6759 Comm: syz.5.545 Not tainted 6.1.116-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call trace:
dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:284 [inline]
print_report+0x174/0x4c0 mm/kasan/report.c:395
kasan_report+0xd4/0x130 mm/kasan/report.c:495
__asan_report_load1_noabort+0x2c/0x38 mm/kasan/report_generic.c:348
__fb_pad_aligned_buffer include/linux/fb.h:655 [inline]
bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
bit_putcs+0x9b8/0xe30 drivers/video/fbdev/core/bitblit.c:185
fbcon_putcs+0x318/0x4e8 drivers/video/fbdev/core/fbcon.c:1284
do_update_region+0x2ec/0x5f8 drivers/tty/vt/vt.c:666
update_region+0x1e0/0x478 drivers/tty/vt/vt.c:694
vcs_write+0x988/0x1160 drivers/tty/vt/vc_screen.c:698
vfs_write+0x2a4/0x91c fs/read_write.c:582
ksys_write+0x15c/0x26c fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the variable:
fontdata_8x16+0x12f0/0x1480

The buggy address belongs to the virtual mapping at
[ffff800012390000, ffff800015570000) created by:
map_kernel+0x1b0/0x4a8 arch/arm64/mm/mmu.c:786

The buggy address belongs to the physical page:
page:000000001fb0536f refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1a86f7
flags: 0x5ffc00000001000(reserved|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000001000 fffffc0005a1bdc8 fffffc0005a1bdc8 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8000128f7400: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
ffff8000128f7480: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
>ffff8000128f7500: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
^
ffff8000128f7580: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
ffff8000128f7600: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.