Forwarded: Re: [syzbot] [hfs?] kernel BUG in hfs_new_inode

[syzbot <syzbot+17cc9bb6d8d69b4139f0@syzkaller.appspotmail.com>]

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Subject: Re: [syzbot] [hfs?] kernel BUG in hfs_new_inode
Author: ekffu200098@gmail.com

#syz test

On Thu, Oct 23, 2025 at 2:35 PM syzbot
<syzbot+17cc9bb6d8d69b4139f0@syzkaller.appspotmail.com> wrote:
>
> 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 <slava@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+17cc9bb6d8d69b4139f0@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
>
>
> ---
> 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 syzkaller@googlegroups.com.
>
> syzbot will keep track of this issue. See:
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> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
> If the report is already addressed, let syzbot know by replying with:
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>
> If you want syzbot to run the reproducer, reply with:
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>
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>
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>
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