ocfs2: add boundary check to ocfs2_check_dir_entry()

ocfs2: add boundary check to ocfs2_check_dir_entry()

In 'ocfs2_check_dir_entry()', add extra check whether at least the
smallest possible dirent may be located at the specified offset within
bh's data, thus preventing an out-of-bounds accesses below.

Link: https://lkml.kernel.org/r/20251013062826.122586-1-dmantipov@yandex.ru
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Reported-by: syzbot+b20bbf680bb0f2ecedae@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b20bbf680bb0f2ecedae
Reviewed-by: Heming Zhao <heming.zhao@suse.com>
Cc: Joseph Qi <jiangqi903@gmail.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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>