------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dtree.c:3700:8
index -1 is out of range for type 'struct dtslot[128]'
CPU: 0 UID: 0 PID: 6219 Comm: syz.0.49 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:233
 __ubsan_handle_out_of_bounds+0xe8/0xf0 lib/ubsan.c:455
 dtInsertEntry+0x936/0x1430 fs/jfs/jfs_dtree.c:3700
 dtSplitPage+0x290b/0x37c0 fs/jfs/jfs_dtree.c:1596
 dtSplitUp fs/jfs/jfs_dtree.c:1092 [inline]
 dtInsert+0x10a4/0x5f10 fs/jfs/jfs_dtree.c:871
 jfs_mkdir+0x783/0xb00 fs/jfs/namei.c:270
 vfs_mkdir+0x75d/0x870 fs/namei.c:5139
 do_mkdirat+0x281/0x4c0 fs/namei.c:5173
 __do_sys_mkdir fs/namei.c:5200 [inline]
 __se_sys_mkdir fs/namei.c:5198 [inline]
 __x64_sys_mkdir+0x6c/0x80 fs/namei.c:5198
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd33a6aaeb9
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:00007fd338906028 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00007fd33a925fa0 RCX: 00007fd33a6aaeb9
RDX: 0000000000000000 RSI: 0000000000000024 RDI: 0000200000000100
RBP: 00007fd33a718c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd33a926038 R14: 00007fd33a925fa0 R15: 00007ffd9eb1eab8
 </TASK>
---[ end trace ]---