CVE-2024-26826

In the Linux kernel, the following vulnerability has been resolved: mptcp:
fix data re-injection from stale subflow When the MPTCP PM detects that a
subflow is stale, all the packet scheduler must re-inject all the
mptcp-level unacked data. To avoid acquiring unneeded locks, it first try
to check if any unacked data is present at all in the RTX queue, but such
check is currently broken, as it uses TCP-specific helper on an MPTCP
socket. Funnily enough fuzzers and static checkers are happy, as the
accessed memory still belongs to the mptcp_sock struct, and even from a
functional perspective the recovery completed successfully, as the
short-cut test always failed. A recent unrelated TCP change - commit
d5fed5addb2b (“tcp: reorganize tcp_sock fast path variables”) - exposed the
issue, as the tcp field reorganization makes the mptcp code always skip the
re-inection. Fix the issue dropping the bogus call: we are on a slow path,
the early optimization proved once again to be evil.