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Message-Id: <20240223-upstream-net-next-20240223-misc-improvements-v1-3-b6c8a10396bd@kernel.org>
Date: Fri, 23 Feb 2024 21:17:55 +0100
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>,
Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-kernel@...r.kernel.org, "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
Subject: [PATCH net-next 3/8] mptcp: check the protocol in tcp_sk() with
DEBUG_NET
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@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
net/mptcp/protocol.h | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index f89b197a9f92..026ed360bd72 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -348,6 +348,16 @@ static inline void msk_owned_by_me(const struct mptcp_sock *msk)
sock_owned_by_me((const struct sock *)msk);
}
+#ifdef CONFIG_DEBUG_NET
+/* MPTCP-specific: we might (indirectly) call this helper with the wrong sk */
+#undef tcp_sk
+#define tcp_sk(ptr) ({ \
+ typeof(ptr) _ptr = (ptr); \
+ WARN_ON(_ptr->sk_protocol != IPPROTO_TCP); \
+ container_of_const(_ptr, struct tcp_sock, inet_conn.icsk_inet.sk); \
+})
+#endif
+
#define mptcp_sk(ptr) container_of_const(ptr, struct mptcp_sock, sk.icsk_inet.sk)
/* the msk socket don't use the backlog, also account for the bulk
--
2.43.0
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