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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f2ddafa93a25 Linux 6.1.166
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16734cf6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=54013d63871351b9f5de
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/28fc2cbac5cf/disk-f2ddafa9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b17a5a214fbc/vmlinux-f2ddafa9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c2564b1203e5/Image-f2ddafa9.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+54013d...@syzkaller.appspotmail.com

NILFS (loop2): recovery complete
Unable to handle kernel paging request at virtual address dfff800000000006
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
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
[dfff800000000006] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 6036 Comm: syz.2.608 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : nilfs_mdt_save_to_shadow_map+0x134/0x1b4 fs/nilfs2/mdt.c:549
lr : nilfs_mdt_save_to_shadow_map+0xcc/0x1b4 fs/nilfs2/mdt.c:545
sp : ffff8000211176c0
x29: ffff8000211176c0 x28: ffff700004222ef0 x27: dfff800000000000
x26: ffff0000fea2c678 x25: ffff800021117a40 x24: ffff0000e2361490
x23: dfff800000000000 x22: 0000000000000030 x21: ffff0000e2361d20
x20: ffff0000f5a7d540 x19: ffff0000e2360e28 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082d7ca0 x15: 0000000000000002
x14: 0000000000000406 x13: 0000000000ff0100 x12: 0000000000ff0100
x11: ff00800009c4f514 x10: 0000000000000002 x9 : ffff0000cc981bc0
x8 : 0000000000000006 x7 : ffff8000086f165c x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000002
x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
nilfs_mdt_save_to_shadow_map+0x134/0x1b4 fs/nilfs2/mdt.c:549
nilfs_clean_segments+0x124/0x870 fs/nilfs2/segment.c:2512
nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:940 [inline]
nilfs_ioctl+0x22c0/0x2660 fs/nilfs2/ioctl.c:1304
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+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 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
Code: 97b258b5 f94002c8 9100c116 d343fec8 (38776908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 97b258b5 bl 0xfffffffffec962d4
4: f94002c8 ldr x8, [x22]
8: 9100c116 add x22, x8, #0x30
c: d343fec8 lsr x8, x22, #3
* 10: 38776908 ldrb w8, [x8, x23] <-- trapping instruction


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: f2ddafa93a25 Linux 6.1.166
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=130934ba580000

kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=54013d63871351b9f5de
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16574ada580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17369a16580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/28fc2cbac5cf/disk-f2ddafa9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b17a5a214fbc/vmlinux-f2ddafa9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c2564b1203e5/Image-f2ddafa9.gz.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/2937c4abd246/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+54013d...@syzkaller.appspotmail.com

NILFS (loop0): invalid segment: Checksum error in segment payload
NILFS (loop0): trying rollback from an earlier position
NILFS (loop0): recovery complete

Unable to handle kernel paging request at virtual address dfff800000000006
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
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
[dfff800000000006] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:

CPU: 0 PID: 4491 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : nilfs_mdt_save_to_shadow_map+0x134/0x1b4 fs/nilfs2/mdt.c:549
lr : nilfs_mdt_save_to_shadow_map+0xcc/0x1b4 fs/nilfs2/mdt.c:545

sp : ffff8000210e76c0
x29: ffff8000210e76c0 x28: ffff70000421cef0 x27: dfff800000000000
x26: ffff0000d2f20678 x25: ffff8000210e7a40 x24: ffff0000e5bd07c0
x23: dfff800000000000 x22: 0000000000000030 x21: ffff0000e5bd1050
x20: ffff0000de86ed40 x19: ffff0000e5bd0158 x18: 0000000000000000
x17: ffff800018349000 x16: ffff8000082d7ca0 x15: 0000000000000000

x14: 0000000000000406 x13: 0000000000ff0100 x12: 0000000000ff0100

x11: ff00800009c4f514 x10: 0000000000000000 x9 : ffff0000d22f1bc0

If you want syzbot to run the reproducer, reply with:
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