[v6.1] BUG: unable to handle kernel paging request in bit_putcs

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6c44e13dc284 Linux 6.1.46
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16232b37a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=b2c187b22ae203e6
dashboard link: https://syzkaller.appspot.com/bug?extid=525a735fc85a5b1d59a7
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/b0d18761f322/disk-6c44e13d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/13bec23c6ccd/vmlinux-6c44e13d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c3754b46d4b8/Image-6c44e13d.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+525a73...@syzkaller.appspotmail.com

Unable to handle kernel paging request at virtual address dfff80000000005e
KASAN: null-ptr-deref in range [0x00000000000002f0-0x00000000000002f7]
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
[dfff80000000005e] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 30092 Comm: syz-executor.5 Not tainted 6.1.46-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __fb_pad_aligned_buffer include/linux/fb.h:655 [inline]
pc : bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
pc : bit_putcs+0x958/0xe30 drivers/video/fbdev/core/bitblit.c:185
lr : __fb_pad_aligned_buffer include/linux/fb.h:652 [inline]
lr : bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
lr : bit_putcs+0x93c/0xe30 drivers/video/fbdev/core/bitblit.c:185
sp : ffff80001f837480
x29: ffff80001f837690 x28: 00000000000002f0 x27: ffff0000cdd6ca30
x26: ffff0000cdd6ca30 x25: 000000000000000f x24: dfff800000000000
x23: 0000000000000028 x22: 0000000000000000 x21: 0000000000000000
x20: ffff0000c0031440 x19: 00000000000002f0 x18: 1fffe000368a9f76
x17: ffff8000158ad000 x16: ffff80001206ba40 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000003 x12: 00000000ffffffff
x11: ff8080000b084fd0 x10: 0000000000000000 x9 : 0000000000000000
x8 : 000000000000005e x7 : 0000000000000000 x6 : 0000000000000007
x5 : 0000000000000000 x4 : 0000000000000008 x3 : ffff80000b084748
x2 : 0000000000000280 x1 : 0000000000000010 x0 : 0000000000000000
Call trace:
__fb_pad_aligned_buffer include/linux/fb.h:655 [inline]
bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
bit_putcs+0x958/0xe30 drivers/video/fbdev/core/bitblit.c:185
fbcon_putcs+0x318/0x4e8 drivers/video/fbdev/core/fbcon.c:1282
do_update_region+0x42c/0x5f8 drivers/tty/vt/vt.c:676
redraw_screen+0x82c/0xd54 drivers/tty/vt/vt.c:1035
fbcon_modechanged+0x9f4/0x1090 drivers/video/fbdev/core/fbcon.c:2709
fbcon_update_vcs+0x3c/0x4c drivers/video/fbdev/core/fbcon.c:2754
do_fb_ioctl+0xb40/0xe34 drivers/video/fbdev/core/fbmem.c:1127
fb_ioctl+0xec/0x134 drivers/video/fbdev/core/fbmem.c:1204
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
__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:142
do_el0_svc+0x64/0x218 arch/arm64/kernel/syscall.c:206
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:581
Code: 51000679 aa1c03f3 d343fe68 12000a69 (38f86908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 51000679 sub w25, w19, #0x1
4: aa1c03f3 mov x19, x28
8: d343fe68 lsr x8, x19, #3
c: 12000a69 and w9, w19, #0x7
* 10: 38f86908 ldrsb w8, [x8, x24] <-- trapping instruction


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite bug's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 6c44e13dc284 Linux 6.1.46
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=110e965fa80000

kernel config: https://syzkaller.appspot.com/x/.config?x=b2c187b22ae203e6
dashboard link: https://syzkaller.appspot.com/bug?extid=525a735fc85a5b1d59a7
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1239c45ba80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=169dc0d3a80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b0d18761f322/disk-6c44e13d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/13bec23c6ccd/vmlinux-6c44e13d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c3754b46d4b8/Image-6c44e13d.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+525a73...@syzkaller.appspotmail.com

Unable to handle kernel paging request at virtual address dfff800000000040
KASAN: null-ptr-deref in range [0x0000000000000200-0x0000000000000207]

Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0

[dfff800000000040] address between user and kernel address ranges

Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:

CPU: 1 PID: 4223 Comm: syz-executor265 Not tainted 6.1.46-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __fb_pad_aligned_buffer include/linux/fb.h:655 [inline]
pc : bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
pc : bit_putcs+0x958/0xe30 drivers/video/fbdev/core/bitblit.c:185
lr : __fb_pad_aligned_buffer include/linux/fb.h:652 [inline]
lr : bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
lr : bit_putcs+0x93c/0xe30 drivers/video/fbdev/core/bitblit.c:185

sp : ffff80001dcd7480
x29: ffff80001dcd7690 x28: 0000000000000200 x27: ffff0000cdd80000
x26: ffff0000cdd80000 x25: 000000000000000f x24: dfff800000000000
x23: 0000000000000080 x22: 0000000000000000 x21: 0000000000000000
x20: ffff0000c0031440 x19: 0000000000000200 x18: 1fffe000368adf76

x17: ffff8000158ad000 x16: ffff80001206ba40 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000003 x12: 00000000ffffffff
x11: ff8080000b084fd0 x10: 0000000000000000 x9 : 0000000000000000

x8 : 0000000000000040 x7 : 0000000000000000 x6 : 0000000000000007

x5 : 0000000000000000 x4 : 0000000000000008 x3 : ffff80000b084748

x2 : 0000000000000800 x1 : 0000000000000010 x0 : 0000000000000000

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 2f91a96b892fab2f2543b4a55740c5bee36b1a6b
Author: Jiri Slaby (SUSE) <jiri...@kernel.org>
Date: Thu Feb 8 11:44:11 2024 +0000

fbcon: always restore the old font data in fbcon_do_set_font()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1564bfc3180000
start commit: e7cddbb41b63 Linux 6.1.67
git tree: linux-6.1.y
kernel config: https://syzkaller.appspot.com/x/.config?x=4d75c4ebe0b479d3
dashboard link: https://syzkaller.appspot.com/bug?extid=525a735fc85a5b1d59a7
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=153542a2e80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fd37dee80000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: fbcon: always restore the old font data in fbcon_do_set_font()

For information about bisection process see: https://goo.gl/tpsmEJ#bisection