[syzbot] [hfs?] kernel BUG in hfs_new_inode

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 552c50713f27 Merge tag 'vfio-v6.18-rc3' of https://github...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1231d734580000
kernel config: https://syzkaller.appspot.com/x/.config?x=216353986aa62c5d
dashboard link: https://syzkaller.appspot.com/bug?extid=17cc9bb6d8d69b4139f0
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10e953e2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=176d7c58580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/822137407e34/disk-552c5071.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c352dbdc77fe/vmlinux-552c5071.xz
kernel image: https://storage.googleapis.com/syzbot-assets/96bd9d9f8c50/bzImage-552c5071.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/d008a2751bbd/mount_0.gz

The issue was bisected to:

commit a06ec283e125e334155fe13005c76c9f484ce759
Author: Viacheslav Dubeyko <sl...@dubeyko.com>
Date: Tue Jun 10 23:16:09 2025 +0000

hfs: add logic of correcting a next unused CNID

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11b4e3e2580000
final oops: https://syzkaller.appspot.com/x/report.txt?x=13b4e3e2580000
console output: https://syzkaller.appspot.com/x/log.txt?x=15b4e3e2580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+17cc9b...@syzkaller.appspotmail.com
Fixes: a06ec283e125 ("hfs: add logic of correcting a next unused CNID")

loop0: detected capacity change from 0 to 64
hfs: unable to loca[ 123.243188][ T5988] hfs: unable to locate alternate MDB
hfs: continuing without an alternate MDB
------------[ cut here ]------------
kernel BUG at fs/hfs/inode.c:222!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 5988 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:hfs_new_inode+0xbc4/0xbd0 fs/hfs/inode.c:222
Code: 89 f1 80 e1 07 fe c1 38 c1 0f 8c 15 fa ff ff 4c 89 f7 e8 0f 6f 8b ff e9 08 fa ff ff e8 b5 b7 29 ff 90 0f 0b e8 ad b7 29 ff 90 <0f> 0b e8 a5 b7 29 ff 90 0f 0b 66 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900040af848 EFLAGS: 00010293
RAX: ffffffff829555d3 RBX: ffff8880335088c8 RCX: ffff888026d23c00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed1005214608 R12: ffff8880290a3000
R13: 1ffff110073d90f3 R14: 0000000100000000 R15: ffff8880335088c8
FS: 00007f6c84dde6c0(0000) GS:ffff888126cc2000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e263fff CR3: 000000003276a000 CR4: 00000000003526f0
Call Trace:
<TASK>
hfs_create+0x2a/0xe0 fs/hfs/dir.c:198
lookup_open fs/namei.c:3796 [inline]
open_last_lookups fs/namei.c:3895 [inline]
path_openat+0x1500/0x3840 fs/namei.c:4131
do_filp_open+0x1fa/0x410 fs/namei.c:4161
do_sys_openat2+0x121/0x1c0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6c8576efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6c84dde038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f6c859c5fa0 RCX: 00007f6c8576efc9
RDX: 0000000000000042 RSI: 00002000000002c0 RDI: ffffffffffffff9c
RBP: 00007f6c857f1f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000058 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6c859c6038 R14: 00007f6c859c5fa0 R15: 00007fffc4216518
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:hfs_new_inode+0xbc4/0xbd0 fs/hfs/inode.c:222
Code: 89 f1 80 e1 07 fe c1 38 c1 0f 8c 15 fa ff ff 4c 89 f7 e8 0f 6f 8b ff e9 08 fa ff ff e8 b5 b7 29 ff 90 0f 0b e8 ad b7 29 ff 90 <0f> 0b e8 a5 b7 29 ff 90 0f 0b 66 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900040af848 EFLAGS: 00010293
RAX: ffffffff829555d3 RBX: ffff8880335088c8 RCX: ffff888026d23c00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed1005214608 R12: ffff8880290a3000
R13: 1ffff110073d90f3 R14: 0000000100000000 R15: ffff8880335088c8
FS: 00007f6c84dde6c0(0000) GS:ffff888126cc2000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e263fff CR3: 000000003276a000 CR4: 00000000003526f0


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***

Subject: Re: [syzbot] [hfs?] kernel BUG in hfs_new_inode
Author: ekffu...@gmail.com

#syz test

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[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in hfs_new_inode

loop0: detected capacity change from 0 to 64

hfs: unable to locate alternate MDB
hfs: continuing without an alternate MDB
------------[ cut here ]------------
kernel BUG at fs/hfs/inode.c:222!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI

CPU: 0 UID: 0 PID: 6697 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:hfs_new_inode+0xbc4/0xbd0 fs/hfs/inode.c:222

Code: 89 f1 80 e1 07 fe c1 38 c1 0f 8c 15 fa ff ff 4c 89 f7 e8 0f 6d 8b ff e9 08 fa ff ff e8 c5 b5 29 ff 90 0f 0b e8 bd b5 29 ff 90 <0f> 0b e8 b5 b5 29 ff 90 0f 0b 66 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90003b37848 EFLAGS: 00010293
RAX: ffffffff829557c3 RBX: ffff88803a419748 RCX: ffff888026245a00

RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000

R10: dffffc0000000000 R11: ffffed1004f94608 R12: ffff888027ca3000
R13: 1ffff110068414f3 R14: 0000000100000000 R15: ffff88803a419748
FS: 00007f166458e6c0(0000) GS:ffff888126bc2000(0000) knlGS:0000000000000000

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

CR2: 0000001b31463fff CR3: 000000003ad7a000 CR4: 00000000003526f0

Call Trace:
<TASK>
hfs_create+0x2a/0xe0 fs/hfs/dir.c:198
lookup_open fs/namei.c:3796 [inline]
open_last_lookups fs/namei.c:3895 [inline]
path_openat+0x1500/0x3840 fs/namei.c:4131
do_filp_open+0x1fa/0x410 fs/namei.c:4161
do_sys_openat2+0x121/0x1c0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f1664f1efc9

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007f166458e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f1665175fa0 RCX: 00007f1664f1efc9

RDX: 0000000000000042 RSI: 00002000000002c0 RDI: ffffffffffffff9c

RBP: 00007f1664fa1f91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000058 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f1665176038 R14: 00007f1665175fa0 R15: 00007ffeb72a90b8

</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:hfs_new_inode+0xbc4/0xbd0 fs/hfs/inode.c:222

Code: 89 f1 80 e1 07 fe c1 38 c1 0f 8c 15 fa ff ff 4c 89 f7 e8 0f 6d 8b ff e9 08 fa ff ff e8 c5 b5 29 ff 90 0f 0b e8 bd b5 29 ff 90 <0f> 0b e8 b5 b5 29 ff 90 0f 0b 66 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90003b37848 EFLAGS: 00010293
RAX: ffffffff829557c3 RBX: ffff88803a419748 RCX: ffff888026245a00

RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000

R10: dffffc0000000000 R11: ffffed1004f94608 R12: ffff888027ca3000
R13: 1ffff110068414f3 R14: 0000000100000000 R15: ffff88803a419748
FS: 00007f166458e6c0(0000) GS:ffff888126bc2000(0000) knlGS:0000000000000000

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

CR2: 0000001b31463fff CR3: 000000003ad7a000 CR4: 00000000003526f0


Tested on:

commit: 43e9ad0c Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=128eb734580000

kernel config: https://syzkaller.appspot.com/x/.config?x=216353986aa62c5d
dashboard link: https://syzkaller.appspot.com/bug?extid=17cc9bb6d8d69b4139f0
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=14dd5b04580000