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[net-next,4/8] mptcp: check the protocol in mptcp_sk() with DEBUG_NET

Message ID 20240223-upstream-net-next-20240223-misc-improvements-v1-4-b6c8a10396bd@kernel.org
State Accepted
Commit 14d29ec5302caac945267b9586fad01ecddc700c
Headers show
Series mptcp: various small improvements | expand

Commit Message

Matthieu Baerts (NGI0) Feb. 23, 2024, 8:17 p.m. UTC 
Fuzzers and static checkers might not detect when mptcp_sk() is used
with a non mptcp_sock structure.

This is similar to the parent commit, where it is easy to use mptcp_sk()
with a TCP sock, e.g. with a subflow sk.

So a new simple check is done when CONFIG_DEBUG_NET is enabled to tell
kernel devs when a non-MPTCP socket is being used as an MPTCP one.
'mptcp_sk()' macro is then defined differently: with an extra WARN to
complain when an unexpected socket is being used.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
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Patch

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 026ed360bd72..051b100d9403 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -356,9 +356,15 @@  static inline void msk_owned_by_me(const struct mptcp_sock *msk)
 	WARN_ON(_ptr->sk_protocol != IPPROTO_TCP);				\
 	container_of_const(_ptr, struct tcp_sock, inet_conn.icsk_inet.sk);	\
 })
-#endif
+#define mptcp_sk(ptr) ({						\
+	typeof(ptr) _ptr = (ptr);					\
+	WARN_ON(_ptr->sk_protocol != IPPROTO_MPTCP);			\
+	container_of_const(_ptr, struct mptcp_sock, sk.icsk_inet.sk);	\
+})
 
+#else /* !CONFIG_DEBUG_NET */
 #define mptcp_sk(ptr) container_of_const(ptr, struct mptcp_sock, sk.icsk_inet.sk)
+#endif
 
 /* the msk socket don't use the backlog, also account for the bulk
  * free memory