[syzbot] [ocfs2?] UBSAN: array-index-out-of-bounds in ocfs2_block_group_fill

[syzbot <syzbot+77026564530dbc29b854@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    52ba76324a9d Add linux-next specific files for 20251013
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=157d3b34580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=99cb6b007a8889ef
dashboard link: https://syzkaller.appspot.com/bug?extid=77026564530dbc29b854
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=15039dcd980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15ad9542580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1729256319ee/disk-52ba7632.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a3152cfcba7c/vmlinux-52ba7632.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4065a3b3d959/bzImage-52ba7632.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/d98ffa49f949/mount_0.gz
  fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=1510f304580000)

The issue was bisected to:

commit aa545adbe491402cf1e664f6be0a799ed69d9946
Author: Dmitry Antipov <dmantipov@yandex.ru>
Date:   Tue Oct 7 12:35:26 2025 +0000

    ocfs2: annotate flexible array members with __counted_by_le()

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11575542580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=13575542580000
console output: https://syzkaller.appspot.com/x/log.txt?x=15575542580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+77026564530dbc29b854@syzkaller.appspotmail.com
Fixes: aa545adbe491 ("ocfs2: annotate flexible array members with __counted_by_le()")

         option from the mount to silence this warning.
=======================================================
JBD2: Ignoring recovery information on journal
ocfs2: Mounting device (7,0) on (node local, slot 0) with ordered data mode.
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/ocfs2/suballoc.c:380:22
index 0 is out of range for type 'struct ocfs2_chain_rec[] __counted_by(cl_count)' (aka 'struct ocfs2_chain_rec[]')
CPU: 0 UID: 0 PID: 6052 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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_block_group_fill+0x938/0xb30 fs/ocfs2/suballoc.c:380
 ocfs2_block_group_alloc_contig fs/ocfs2/suballoc.c:454 [inline]
 ocfs2_block_group_alloc fs/ocfs2/suballoc.c:699 [inline]
 ocfs2_reserve_suballoc_bits+0x117d/0x4680 fs/ocfs2/suballoc.c:834
 ocfs2_reserve_new_metadata_blocks+0x403/0x940 fs/ocfs2/suballoc.c:984
 ocfs2_expand_inline_dir fs/ocfs2/dir.c:2853 [inline]
 ocfs2_extend_dir+0xc76/0x4870 fs/ocfs2/dir.c:3215
 ocfs2_prepare_dir_for_insert+0x2fdf/0x54b0 fs/ocfs2/dir.c:4320
 ocfs2_mknod+0x819/0x2050 fs/ocfs2/namei.c:297
 ocfs2_mkdir+0x191/0x440 fs/ocfs2/namei.c:659
 vfs_mkdir+0x306/0x510 fs/namei.c:4453
 do_mkdirat+0x247/0x590 fs/namei.c:4486
 __do_sys_mkdirat fs/namei.c:4503 [inline]
 __se_sys_mkdirat fs/namei.c:4501 [inline]
 __x64_sys_mkdirat+0x87/0xa0 fs/namei.c:4501
 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: 0033:0x7f0917d8d617
Code: 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 02 01 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:00007fff863b0218 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007fff863b02a0 RCX: 00007f0917d8d617
RDX: 00000000000001ff RSI: 0000200000000680 RDI: 00000000ffffff9c
RBP: 0000200000000080 R08: 0000200000000140 R09: 0000000000000000
R10: 0000200000000080 R11: 0000000000000246 R12: 0000200000000680
R13: 00007fff863b0260 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
---[ end trace ]---


---
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