[syzbot] [ocfs2?] UBSAN: array-index-out-of-bounds in __ocfs2_find_path

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d358e5254674 Merge tag 'for-6.19/dm-changes' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15800592580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f315601b98a91c0b
dashboard link: https://syzkaller.appspot.com/bug?extid=151afab124dfbc5f15e6
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=148d91c2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15c3161a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/605b74c6e6cd/disk-d358e525.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ec0e108fb585/vmlinux-d358e525.xz
kernel image: https://storage.googleapis.com/syzbot-assets/29e316e5a13d/bzImage-d358e525.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/2f95504bd292/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=14ec261a580000)

Bisection is inconclusive: the first bad commit could be any of:

2f26f58df041 ocfs2: annotate flexible array members with __counted_by_le()
cd4eaccc00d7 treewide: drop outdated compiler version remarks in Kconfig help texts
1b34743c31fe ocfs2: add extra consistency check to ocfs2_dx_dir_lookup_rec()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=109551c2580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+151afa...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/ocfs2/alloc.c:1838:11
index 0 is out of range for type 'struct ocfs2_extent_rec[] __counted_by(l_count)' (aka 'struct ocfs2_extent_rec[]')
CPU: 0 UID: 0 PID: 6062 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
ubsan_epilogue+0xa/0x40 lib/ubsan.c:233
__ubsan_handle_out_of_bounds+0xe9/0xf0 lib/ubsan.c:455
__ocfs2_find_path+0x606/0xa40 fs/ocfs2/alloc.c:1838
ocfs2_find_leaf+0xab/0x1c0 fs/ocfs2/alloc.c:1946
ocfs2_get_clusters_nocache+0x172/0xc60 fs/ocfs2/extent_map.c:418
ocfs2_get_clusters+0x505/0xa70 fs/ocfs2/extent_map.c:631
ocfs2_extent_map_get_blocks+0x202/0x6a0 fs/ocfs2/extent_map.c:678
ocfs2_read_virt_blocks+0x286/0x930 fs/ocfs2/extent_map.c:1001
ocfs2_read_dir_block fs/ocfs2/dir.c:521 [inline]
ocfs2_find_entry_el fs/ocfs2/dir.c:728 [inline]
ocfs2_find_entry+0x3e4/0x2090 fs/ocfs2/dir.c:1120
ocfs2_find_files_on_disk+0xdf/0x310 fs/ocfs2/dir.c:2023
ocfs2_lookup_ino_from_name+0x52/0x100 fs/ocfs2/dir.c:2045
_ocfs2_get_system_file_inode fs/ocfs2/sysfile.c:136 [inline]
ocfs2_get_system_file_inode+0x326/0x770 fs/ocfs2/sysfile.c:112
ocfs2_init_global_system_inodes+0x319/0x660 fs/ocfs2/super.c:461
ocfs2_initialize_super fs/ocfs2/super.c:2196 [inline]
ocfs2_fill_super+0x4432/0x65b0 fs/ocfs2/super.c:993
get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
vfs_get_tree+0x92/0x2a0 fs/super.c:1751
fc_mount fs/namespace.c:1199 [inline]
do_new_mount_fc fs/namespace.c:3636 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3712
do_mount fs/namespace.c:4035 [inline]
__do_sys_mount fs/namespace.c:4224 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4201
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6175f30eea
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007ffefc9145f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffefc914680 RCX: 00007f6175f30eea
RDX: 0000200000004440 RSI: 0000200000000340 RDI: 00007ffefc914640
RBP: 0000200000004440 R08: 00007ffefc914680 R09: 0000000000004000
R10: 0000000000004000 R11: 0000000000000246 R12: 0000200000000340
R13: 00007ffefc914640 R14: 0000000000004463 R15: 0000200000000300
</TASK>
---[ end trace ]---


---
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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup