ocfs2: validate inline data i_size during inode read

When reading an inode from disk, ocfs2_validate_inode_block() performs
various sanity checks but does not validate the size of inline data. If
the filesystem is corrupted, an inode's i_size can exceed the actual
inline data capacity (id_count).

This causes ocfs2_dir_foreach_blk_id() to iterate beyond the inline data
buffer, triggering a use-after-free when accessing directory entries from
freed memory.

In the syzbot report:
- i_size was 1099511627576 bytes (~1TB)
- Actual inline data capacity (id_count) is typically <256 bytes
- A garbage rec_len (54648) caused ctx->pos to jump out of bounds
- This triggered a UAF in ocfs2_check_dir_entry()

Fix by adding a validation check in ocfs2_validate_inode_block() to ensure
inodes with inline data have i_size <= id_count. This catches the
corruption early during inode read and prevents all downstream code from
operating on invalid data.

Link: https://lkml.kernel.org/r/20251212052132.16750-1-kartikey406@gmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Reported-by: syzbot+c897823f699449cc3eb4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
Tested-by: syzbot+c897823f699449cc3eb4@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/20251211115231.3560028-1-kartikey406@gmail.com/T/ [v1]
Link: https://lore.kernel.org/all/20251212040400.6377-1-kartikey406@gmail.com/T/ [v2]
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>