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 --- 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