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

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: [ceph] parse_longname(): strrchr() expects NUL-terminated string ... and parse_longname() is not guaranteed that. That's the reason why it uses kmemdup_nul() to build the argument for kstrtou64(); the problem is, kstrtou64() is not the only thing that need it. Just get a NUL-terminated copy of the entire thing and be done with that...

References

• https://git.kernel.org/stable/c/bb80f7618832d26f7e395f52f82b1dac76223e5f
• https://git.kernel.org/stable/c/3145b2b11492d61c512bbc59660bb823bc757f48
• https://git.kernel.org/stable/c/493479af8af3ab907f49e99323777d498a4fbd2b
• https://git.kernel.org/stable/c/101841c38346f4ca41dc1802c867da990ffb32eb