[v6.6] general protection fault in nilfs_mdt_save_to_shadow_map

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8cee53b8eaeb Linux 6.6.134
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=134281ba580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=78987da922319afcebc1
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4c0eb6df7b4a/disk-8cee53b8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/38626ee912e4/vmlinux-8cee53b8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/646a84f3433a/bzImage-8cee53b8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+78987d...@syzkaller.appspotmail.com

NILFS (loop0): invalid segment: Checksum error in segment payload
NILFS (loop0): trying rollback from an earlier position
NILFS (loop0): recovery complete
general protection fault, probably for non-canonical address 0xdffffc0000000008: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000040-0x0000000000000047]
CPU: 1 PID: 9034 Comm: syz.0.918 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:nilfs_mdt_save_to_shadow_map+0x141/0x1c0 fs/nilfs2/mdt.c:549
Code: 3f 4c 8d 63 d8 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 4e 11 9a fe 4d 8b 24 24 49 83 c4 40 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 30 11 9a fe 49 8b 34 24 4c 89 ff
RSP: 0018:ffffc90004c3f808 EFLAGS: 00010202
RAX: 0000000000000008 RBX: ffff88805b1bb498 RCX: 0000000000000002
RDX: ffff888018f41e00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff8e8b14ef R09: 1ffffffff1d1629d
R10: dffffc0000000000 R11: fffffbfff1d1629e R12: 0000000000000040
R13: dffffc0000000000 R14: ffff88802e2ac140 R15: ffff88805b1bc390
FS: 00007f7edd9466c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2d323ffc CR3: 000000002e7b6000 CR4: 00000000003506e0
Call Trace:
<TASK>
nilfs_clean_segments+0x163/0xa40 fs/nilfs2/segment.c:2513
nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:940 [inline]
nilfs_ioctl+0x203f/0x21a0 fs/nilfs2/ioctl.c:1304
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f7edc99c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7edd946028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f7edcc15fa0 RCX: 00007f7edc99c819
RDX: 0000200000000640 RSI: 0000000040786e88 RDI: 0000000000000004
RBP: 00007f7edca32c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7edcc16038 R14: 00007f7edcc15fa0 R15: 00007ffe524f6eb8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:nilfs_mdt_save_to_shadow_map+0x141/0x1c0 fs/nilfs2/mdt.c:549
Code: 3f 4c 8d 63 d8 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 4e 11 9a fe 4d 8b 24 24 49 83 c4 40 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 30 11 9a fe 49 8b 34 24 4c 89 ff
RSP: 0018:ffffc90004c3f808 EFLAGS: 00010202
RAX: 0000000000000008 RBX: ffff88805b1bb498 RCX: 0000000000000002
RDX: ffff888018f41e00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff8e8b14ef R09: 1ffffffff1d1629d
R10: dffffc0000000000 R11: fffffbfff1d1629e R12: 0000000000000040
R13: dffffc0000000000 R14: ffff88802e2ac140 R15: ffff88805b1bc390
FS: 00007f7edd9466c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f54ed3eb4b8 CR3: 000000002e7b6000 CR4: 00000000003506f0
----------------
Code disassembly (best guess), 1 bytes skipped:
0: 4c 8d 63 d8 lea -0x28(%rbx),%r12
4: 4c 89 e0 mov %r12,%rax
7: 48 c1 e8 03 shr $0x3,%rax
b: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1)
10: 74 08 je 0x1a
12: 4c 89 e7 mov %r12,%rdi
15: e8 4e 11 9a fe call 0xfe9a1168
1a: 4d 8b 24 24 mov (%r12),%r12
1e: 49 83 c4 40 add $0x40,%r12
22: 4c 89 e0 mov %r12,%rax
25: 48 c1 e8 03 shr $0x3,%rax
* 29: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2e: 74 08 je 0x38
30: 4c 89 e7 mov %r12,%rdi
33: e8 30 11 9a fe call 0xfe9a1168
38: 49 8b 34 24 mov (%r12),%rsi
3c: 4c 89 ff mov %r15,%rdi


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 8cee53b8eaeb Linux 6.6.134
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=14ff0fca580000

kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=78987da922319afcebc1
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=106224ce580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=171278ce580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4c0eb6df7b4a/disk-8cee53b8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/38626ee912e4/vmlinux-8cee53b8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/646a84f3433a/bzImage-8cee53b8.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/1af150426189/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+78987d...@syzkaller.appspotmail.com

NILFS (loop0): invalid segment: Checksum error in segment payload
NILFS (loop0): trying rollback from an earlier position
NILFS (loop0): recovery complete
general protection fault, probably for non-canonical address 0xdffffc0000000008: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000040-0x0000000000000047]

CPU: 1 PID: 5916 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:nilfs_mdt_save_to_shadow_map+0x141/0x1c0 fs/nilfs2/mdt.c:549
Code: 3f 4c 8d 63 d8 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 4e 11 9a fe 4d 8b 24 24 49 83 c4 40 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 30 11 9a fe 49 8b 34 24 4c 89 ff

RSP: 0018:ffffc90003327808 EFLAGS: 00010202
RAX: 0000000000000008 RBX: ffff88805f478158 RCX: 0000000000000000
RDX: ffff88802b81bc00 RSI: 0000000000000000 RDI: 0000000000000000

RBP: 0000000000000000 R08: ffffffff8e8b14ef R09: 1ffffffff1d1629d
R10: dffffc0000000000 R11: fffffbfff1d1629e R12: 0000000000000040

R13: dffffc0000000000 R14: ffff88802f9ced40 R15: ffff88805f479050
FS: 00005555923a4500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000001b33f63fff CR3: 0000000075181000 CR4: 00000000003506e0

Call Trace:
<TASK>
nilfs_clean_segments+0x163/0xa40 fs/nilfs2/segment.c:2513
nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:940 [inline]
nilfs_ioctl+0x203f/0x21a0 fs/nilfs2/ioctl.c:1304
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7f649879c819

Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007ffe07541978 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6498a15fa0 RCX: 00007f649879c819

RDX: 0000200000000640 RSI: 0000000040786e88 RDI: 0000000000000004

RBP: 00007f6498832c91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f6498a15fac R14: 00007f6498a15fa0 R15: 00007f6498a15fa0

</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:nilfs_mdt_save_to_shadow_map+0x141/0x1c0 fs/nilfs2/mdt.c:549
Code: 3f 4c 8d 63 d8 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 4e 11 9a fe 4d 8b 24 24 49 83 c4 40 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 30 11 9a fe 49 8b 34 24 4c 89 ff

RSP: 0018:ffffc90003327808 EFLAGS: 00010202
RAX: 0000000000000008 RBX: ffff88805f478158 RCX: 0000000000000000
RDX: ffff88802b81bc00 RSI: 0000000000000000 RDI: 0000000000000000

RBP: 0000000000000000 R08: ffffffff8e8b14ef R09: 1ffffffff1d1629d
R10: dffffc0000000000 R11: fffffbfff1d1629e R12: 0000000000000040

R13: dffffc0000000000 R14: ffff88802f9ced40 R15: ffff88805f479050
FS: 00005555923a4500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f3f02448000 CR3: 0000000075181000 CR4: 00000000003506f0

----------------
Code disassembly (best guess), 1 bytes skipped:
0: 4c 8d 63 d8 lea -0x28(%rbx),%r12
4: 4c 89 e0 mov %r12,%rax
7: 48 c1 e8 03 shr $0x3,%rax
b: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1)
10: 74 08 je 0x1a
12: 4c 89 e7 mov %r12,%rdi
15: e8 4e 11 9a fe call 0xfe9a1168
1a: 4d 8b 24 24 mov (%r12),%r12
1e: 49 83 c4 40 add $0x40,%r12
22: 4c 89 e0 mov %r12,%rax
25: 48 c1 e8 03 shr $0x3,%rax
* 29: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2e: 74 08 je 0x38
30: 4c 89 e7 mov %r12,%rdi
33: e8 30 11 9a fe call 0xfe9a1168
38: 49 8b 34 24 mov (%r12),%rsi
3c: 4c 89 ff mov %r15,%rdi


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