mptcp: check the protocol in tcp_sk() with DEBUG_NET

mainline inclusion
from mainline-v6.9-rc1
commit dcc03f270d1e2f4b9715537d8deb734bd019e187
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9VYQ9
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=dcc03f270d1e2f4b9715537d8deb734bd019e187



--------------------------------

Fuzzers and static checkers might not detect when tcp_sk() is used with
a non tcp_sock structure.

This kind of mistake already happened a few times with MPTCP: when
wrongly using TCP-specific helpers with mptcp_sock pointers. On the
other hand, there are many 'tcp_xxx()' helpers that are taking a 'struct
sock' pointer as arguments, and some of them are only looking at fields
from 'struct sock', and nothing from 'struct tcp_sock'. It is then
tempting to use them with a 'struct mptcp_sock'.

So a new simple check is done when CONFIG_DEBUG_NET is enabled to tell
kernel devs when a non-TCP socket is being used as a TCP one. 'tcp_sk()'
macro is then re-defined to add a WARN when an unexpected socket is
being used.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240223-upstream-net-next-20240223-misc-improvements-v1-3-b6c8a10396bd@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>