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@xxxxxxxxxx>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
---
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
