[syzbot] [ocfs2?] kernel BUG in ocfs2_refcount_cal_cow_clusters

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f79e772258df Merge tag 'media/v6.18-1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=151d1ee2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7f967f2c97bd611a
dashboard link: https://syzkaller.appspot.com/bug?extid=6fdd8fa3380730a4b22c
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=16e84458580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=163c9214580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-f79e7722.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9d29501fc412/vmlinux-f79e7722.xz
kernel image: https://storage.googleapis.com/syzbot-assets/773691b45948/bzImage-f79e7722.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/2a53f186d930/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=12731092580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6fdd8f...@syzkaller.appspotmail.com

option from the mount to silence this warning.
=======================================================
ocfs2: Mounting device (7,0) on (node local, slot 0) with ordered data mode.
------------[ cut here ]------------
kernel BUG at fs/ocfs2/refcounttree.c:2678!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5498 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:ocfs2_refcount_cal_cow_clusters+0x12a1/0x12b0 fs/ocfs2/refcounttree.c:2678
Code: 94 6d 8d ba 69 0a 00 00 48 c7 c1 a0 40 8b 8b 4c 8b 4c 24 30 e8 00 51 10 00 90 0f 0b e8 d8 83 17 fe 90 0f 0b e8 d0 83 17 fe 90 <0f> 0b 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90
RSP: 0018:ffffc90002bbf5e0 EFLAGS: 00010293
RAX: ffffffff83a70250 RBX: 1ffff1100863069a RCX: ffff888000bdc900
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90002bbf7a8 R08: 00000000ffffffff R09: ffffc90002bbf85c
R10: 00000000fffffffc R11: 0000000000000000 R12: 0000000000000000
R13: 1ffff1100863069a R14: ffff8880431834d0 R15: 0000000000000000
FS: 0000555579608500(0000) GS:ffff88808d969000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000000b000 CR3: 000000004f2d3000 CR4: 0000000000352ef0
Call Trace:
<TASK>
ocfs2_refcount_cow_hunk fs/ocfs2/refcounttree.c:3385 [inline]
ocfs2_refcount_cow+0x31f/0xc90 fs/ocfs2/refcounttree.c:3467
ocfs2_prepare_inode_for_write fs/ocfs2/file.c:2340 [inline]
ocfs2_file_write_iter+0xe28/0x1d10 fs/ocfs2/file.c:2451
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f386f58eec9
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:00007ffecc491f98 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f386f7e5fa0 RCX: 00007f386f58eec9
RDX: 000000000000001c RSI: 0000200000000100 RDI: 0000000000000005
RBP: 00007f386f611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f386f7e5fa0 R14: 00007f386f7e5fa0 R15: 0000000000000003
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ocfs2_refcount_cal_cow_clusters+0x12a1/0x12b0 fs/ocfs2/refcounttree.c:2678
Code: 94 6d 8d ba 69 0a 00 00 48 c7 c1 a0 40 8b 8b 4c 8b 4c 24 30 e8 00 51 10 00 90 0f 0b e8 d8 83 17 fe 90 0f 0b e8 d0 83 17 fe 90 <0f> 0b 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90
RSP: 0018:ffffc90002bbf5e0 EFLAGS: 00010293
RAX: ffffffff83a70250 RBX: 1ffff1100863069a RCX: ffff888000bdc900
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90002bbf7a8 R08: 00000000ffffffff R09: ffffc90002bbf85c
R10: 00000000fffffffc R11: 0000000000000000 R12: 0000000000000000
R13: 1ffff1100863069a R14: ffff8880431834d0 R15: 0000000000000000
FS: 0000555579608500(0000) GS:ffff88808d969000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000000b000 CR3: 000000004f2d3000 CR4: 0000000000352ef0


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