[v5.15] general protection fault in nilfs_mdt_save_to_shadow_map

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 91d48252ad4b Linux 5.15.202
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13cb8dda580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=edec975ec228553f73a8
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/74e75dfcb812/disk-91d48252.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bfa72aab00f2/vmlinux-91d48252.xz
kernel image: https://storage.googleapis.com/syzbot-assets/47ea72d1c7dc/bzImage-91d48252.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+edec97...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
CPU: 1 PID: 6785 Comm: syz.1.493 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:nilfs_mdt_save_to_shadow_map+0x13d/0x1c0 fs/nilfs2/mdt.c:547
Code: 3f 4c 8d 63 d8 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 c2 1a b1 fe 4d 8b 24 24 49 83 c4 30 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 a4 1a b1 fe 49 8b 34 24 4c 89 ff
RSP: 0018:ffffc900030bf808 EFLAGS: 00010206
RAX: 0000000000000006 RBX: ffff888073369af8 RCX: ffff88802bee1dc0
RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff8d89e36f R09: 1ffffffff1b13c6d
R10: dffffc0000000000 R11: fffffbfff1b13c6e R12: 0000000000000030
R13: dffffc0000000000 R14: ffff88807ca07d40 R15: ffff8880733689e8
FS: 00007f9a361bb6c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b325ffff8 CR3: 000000002a1b8000 CR4: 00000000003526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
nilfs_clean_segments+0x15f/0xa30 fs/nilfs2/segment.c:2514
nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:940 [inline]
nilfs_ioctl+0x2052/0x2190 fs/nilfs2/ioctl.c:1304
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f9a37f61819
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:00007f9a361bb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9a381dafa0 RCX: 00007f9a37f61819
RDX: 0000200000000640 RSI: 0000000040786e88 RDI: 000000000000000c
RBP: 00007f9a37ff7c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9a381db038 R14: 00007f9a381dafa0 R15: 00007fff2155e5d8
</TASK>
Modules linked in:
---[ end trace d6554e10e1f1398a ]---
RIP: 0010:nilfs_mdt_save_to_shadow_map+0x13d/0x1c0 fs/nilfs2/mdt.c:547
Code: 3f 4c 8d 63 d8 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 c2 1a b1 fe 4d 8b 24 24 49 83 c4 30 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 a4 1a b1 fe 49 8b 34 24 4c 89 ff
RSP: 0018:ffffc900030bf808 EFLAGS: 00010206
RAX: 0000000000000006 RBX: ffff888073369af8 RCX: ffff88802bee1dc0
RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff8d89e36f R09: 1ffffffff1b13c6d
R10: dffffc0000000000 R11: fffffbfff1b13c6e R12: 0000000000000030
R13: dffffc0000000000 R14: ffff88807ca07d40 R15: ffff8880733689e8
FS: 00007f9a361bb6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f034c411286 CR3: 000000002a1b8000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
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 c2 1a b1 fe call 0xfeb11adc
1a: 4d 8b 24 24 mov (%r12),%r12
1e: 49 83 c4 30 add $0x30,%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 a4 1a b1 fe call 0xfeb11adc
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: 91d48252ad4b Linux 5.15.202
git tree: linux-5.15.y

console output: https://syzkaller.appspot.com/x/log.txt?x=136935da580000

kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=edec975ec228553f73a8
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=15b49d02580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=176935da580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/74e75dfcb812/disk-91d48252.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bfa72aab00f2/vmlinux-91d48252.xz
kernel image: https://storage.googleapis.com/syzbot-assets/47ea72d1c7dc/bzImage-91d48252.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/3279ad781268/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+edec97...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 4096
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 0xdffffc0000000006: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]

CPU: 1 PID: 4336 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:nilfs_mdt_save_to_shadow_map+0x13d/0x1c0 fs/nilfs2/mdt.c:547
Code: 3f 4c 8d 63 d8 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 c2 1a b1 fe 4d 8b 24 24 49 83 c4 30 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 a4 1a b1 fe 49 8b 34 24 4c 89 ff

RSP: 0018:ffffc9000312f808 EFLAGS: 00010206
RAX: 0000000000000006 RBX: ffff88805c0d0158 RCX: ffff8880226d8000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000

RBP: 0000000000000000 R08: ffffffff8d89e36f R09: 1ffffffff1b13c6d
R10: dffffc0000000000 R11: fffffbfff1b13c6e R12: 0000000000000030

R13: dffffc0000000000 R14: ffff88807df57940 R15: ffff88805c0d1050
FS: 000055557ba43500(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000

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

CR2: 0000001b30e63fff CR3: 000000007d5ec000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
nilfs_clean_segments+0x15f/0xa30 fs/nilfs2/segment.c:2514
nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:940 [inline]
nilfs_ioctl+0x2052/0x2190 fs/nilfs2/ioctl.c:1304
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7fe8ce323819

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:00007ffc881bd9c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe8ce59cfa0 RCX: 00007fe8ce323819
RDX: 0000200000000640 RSI: 0000000040786e88 RDI: 0000000000000004
RBP: 00007fe8ce3b9c91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007fe8ce59cfac R14: 00007fe8ce59cfa0 R15: 00007fe8ce59cfa0
</TASK>
Modules linked in:
---[ end trace 1c1ee43cd0d83265 ]---

RIP: 0010:nilfs_mdt_save_to_shadow_map+0x13d/0x1c0 fs/nilfs2/mdt.c:547
Code: 3f 4c 8d 63 d8 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 c2 1a b1 fe 4d 8b 24 24 49 83 c4 30 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 a4 1a b1 fe 49 8b 34 24 4c 89 ff

RSP: 0018:ffffc9000312f808 EFLAGS: 00010206
RAX: 0000000000000006 RBX: ffff88805c0d0158 RCX: ffff8880226d8000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000

RBP: 0000000000000000 R08: ffffffff8d89e36f R09: 1ffffffff1b13c6d
R10: dffffc0000000000 R11: fffffbfff1b13c6e R12: 0000000000000030

R13: dffffc0000000000 R14: ffff88807df57940 R15: ffff88805c0d1050
FS: 000055557ba43500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000

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

CR2: 00007fdeae5a4000 CR3: 000000007d5ec000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
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 c2 1a b1 fe call 0xfeb11adc
1a: 4d 8b 24 24 mov (%r12),%r12
1e: 49 83 c4 30 add $0x30,%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 a4 1a b1 fe call 0xfeb11adc
38: 49 8b 34 24 mov (%r12),%rsi
3c: 4c 89 ff mov %r15,%rdi


---

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