CVE-2025-38660 [ceph] parse_longname(): strrchr() expects NUL-terminated string

In the Linux kernel, the following vulnerability has been resolved: ceph parselongname: strrchr expects NUL-terminated string ... and parselongname is not guaranteed that. That's the reason why it uses kmemdupnul to build the argument for kstrtou64; the problem is, kstrtou64 is not the only thing...