[Jfs-discussion] [syzbot] [jfs?] kernel BUG in dtSplitRoot

[syzbot <syz...@sy...>]

Hello,

syzbot found the following issue on:

HEAD commit:    1d18101a644e Merge tag 'kernel-6.19-rc1.cred' of git://git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=132812b4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a1db0fea040c2a9f
dashboard link: https://syzkaller.appspot.com/bug?extid=a099d674daa27a9272db
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=14f9e512580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10add512580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-1d18101a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/98f78b52cccd/vmlinux-1d18101a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7a8898061bfb/bzImage-1d18101a.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/1671de9ba119/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=10f9e512580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syz...@sy...

UFO tlock:0xffffc9000152d5e8
BUG at fs/jfs/jfs_dtree.c:1942 assert(dtlck->index == 0)
------------[ cut here ]------------
kernel BUG at fs/jfs/jfs_dtree.c:1942!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5663 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:dtSplitRoot+0x1694/0x16c0 fs/jfs/jfs_dtree.c:1942
Code: e9 49 f3 ff ff e8 2c fc 77 fe 48 c7 c7 e0 88 a4 8b 48 c7 c6 c0 87 a4 8b ba 96 07 00 00 48 c7 c1 60 89 a4 8b e8 3d 01 df fd 90 <0f> 0b e8 05 fc 77 fe 48 c7 c7 e0 88 a4 8b 48 c7 c6 c0 87 a4 8b ba
RSP: 0018:ffffc9000d2972a8 EFLAGS: 00010246
RAX: 0000000000000038 RBX: 0000000000001000 RCX: c529552525a5ed00
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc9000152d6db R08: ffff88801fe24253 R09: 1ffff11003fc484a
R10: dffffc0000000000 R11: ffffed1003fc484b R12: dffffc0000000000
R13: 1ffff920002a5adb R14: 0000000000000002 R15: ffffc9000152d6c0
FS:  0000555582889500(0000) GS:ffff88808d722000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe1757d0e9c CR3: 000000004fc9e000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 dtSplitUp fs/jfs/jfs_dtree.c:1244 [inline]
 dtInsert+0x2525/0x5f40 fs/jfs/jfs_dtree.c:871
 jfs_create+0x6c8/0xa80 fs/jfs/namei.c:137
 lookup_open fs/namei.c:3866 [inline]
 open_last_lookups fs/namei.c:3965 [inline]
 path_openat+0x188f/0x3b80 fs/namei.c:4201
 do_filp_open+0x1fa/0x410 fs/namei.c:4231
 do_sys_openat2+0x121/0x1c0 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_creat fs/open.c:1530 [inline]
 __se_sys_creat fs/open.c:1524 [inline]
 __x64_sys_creat+0x8f/0xc0 fs/open.c:1524
 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: 0033:0x7f94e718f7c9
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:00007ffe798e7728 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007f94e73e5fa0 RCX: 00007f94e718f7c9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000580
RBP: 00007f94e7213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f94e73e5fa0 R14: 00007f94e73e5fa0 R15: 0000000000000002
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dtSplitRoot+0x1694/0x16c0 fs/jfs/jfs_dtree.c:1942
Code: e9 49 f3 ff ff e8 2c fc 77 fe 48 c7 c7 e0 88 a4 8b 48 c7 c6 c0 87 a4 8b ba 96 07 00 00 48 c7 c1 60 89 a4 8b e8 3d 01 df fd 90 <0f> 0b e8 05 fc 77 fe 48 c7 c7 e0 88 a4 8b 48 c7 c6 c0 87 a4 8b ba
RSP: 0018:ffffc9000d2972a8 EFLAGS: 00010246
RAX: 0000000000000038 RBX: 0000000000001000 RCX: c529552525a5ed00
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc9000152d6db R08: ffff88801fe24253 R09: 1ffff11003fc484a
R10: dffffc0000000000 R11: ffffed1003fc484b R12: dffffc0000000000
R13: 1ffff920002a5adb R14: 0000000000000002 R15: ffffc9000152d6c0
FS:  0000555582889500(0000) GS:ffff88808d722000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2ca51ff000 CR3: 000000004fc9e000 CR4: 0000000000352ef0


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