------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dtree.c:3657:9
index 27 is out of range for type 'struct lv[20]'
CPU: 1 UID: 0 PID: 7803 Comm: syz.9.251 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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+0x106d/0x1430 fs/jfs/jfs_dtree.c:3657
 dtSplitPage+0x284c/0x36a0 fs/jfs/jfs_dtree.c:1593
 dtSplitUp fs/jfs/jfs_dtree.c:1089 [inline]
 dtInsert+0x1081/0x5cd0 fs/jfs/jfs_dtree.c:868
 jfs_mkdir+0x783/0xb00 fs/jfs/namei.c:271
 vfs_mkdir+0x40b/0x630 fs/namei.c:5261
 filename_mkdirat+0x289/0x520 fs/namei.c:5294
 __do_sys_mkdirat fs/namei.c:5315 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5312
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa977cbbc47
Code: 00 66 90 48 89 f2 b9 00 01 00 00 48 89 fe bf 9c ff ff ff e9 db f7 ff ff 66 2e 0f 1f 84 00 00 00 00 00 90 b8 02 01 00 00 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:00007fa975f0de58 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007fa975f0dee0 RCX: 00007fa977cbbc47
RDX: 00000000000001ff RSI: 0000200000000440 RDI: 00000000ffffff9c
RBP: 0000200000000080 R08: 0000200000000140 R09: 0000000000000000
R10: 0000200000000080 R11: 0000000000000246 R12: 0000200000000440
R13: 00007fa975f0dea0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
---[ end trace ]---