mptcp: pm: fix ID 0 endp usage after multiple re-creations

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: mptcp: pm: fix ID 0 endp usage after multiple re-creations 'local_addr_used' and 'add_addr_accepted' are decremented for addresses not related to the initial subflow (ID0), because the source and destination addresses of the initial subflows are known from the beginning: they don't count as "additional local address being used" or "ADD_ADDR being accepted". It is then required not to increment them when the entrypoint used by the initial subflow is removed and re-added during a connection. Without this modification, this entrypoint cannot be removed and re-added more than once.

References

• https://git.kernel.org/stable/c/c9c744666f7308a4daba520191e29d395260bcfe
• https://git.kernel.org/stable/c/53e2173172d26c0617b29dd83618b71664bed1fb
• https://git.kernel.org/stable/c/119806ae4e46cf239db8e6ad92bc2fd3daae86dc
• https://git.kernel.org/stable/c/9366922adc6a71378ca01f898c41be295309f044