mptcp: annotate access for msk keys

Both the local and the remote key follow the same locking
schema, put in place the proper ONCE accessors.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/options.c

@@ -689,8 +689,8 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *
 	opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 	if (!echo) {
 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);
-		opts->ahmac = add_addr_generate_hmac(msk->local_key,
-						     msk->remote_key,
+		opts->ahmac = add_addr_generate_hmac(READ_ONCE(msk->local_key),
+						     READ_ONCE(msk->remote_key),
 						     &opts->addr);
 	} else {
 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADDTX);
@@ -792,7 +792,7 @@ static bool mptcp_established_options_fastclose(struct sock *sk,
 
 	*size = TCPOLEN_MPTCP_FASTCLOSE;
 	opts->suboptions |= OPTION_MPTCP_FASTCLOSE;
-	opts->rcvr_key = msk->remote_key;
+	opts->rcvr_key = READ_ONCE(msk->remote_key);
 
 	pr_debug("FASTCLOSE key=%llu", opts->rcvr_key);
 	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSETX);
@@ -1099,8 +1099,8 @@ static bool add_addr_hmac_valid(struct mptcp_sock *msk,
 	if (mp_opt->echo)
 		return true;
 
-	hmac = add_addr_generate_hmac(msk->remote_key,
-				      msk->local_key,
+	hmac = add_addr_generate_hmac(READ_ONCE(msk->remote_key),
+				      READ_ONCE(msk->local_key),
 				      &mp_opt->addr);
 
 	pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
@@ -1147,7 +1147,7 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 
 	if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
 		if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
-		    msk->local_key == mp_opt.rcvr_key) {
+		    READ_ONCE(msk->local_key) == mp_opt.rcvr_key) {
 			WRITE_ONCE(msk->rcv_fastclose, true);
 			mptcp_schedule_work((struct sock *)msk);
 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX);

net/mptcp/protocol.c

@@ -3193,7 +3193,7 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,
 	__mptcp_init_sock(nsk);
 
 	msk = mptcp_sk(nsk);
-	msk->local_key = subflow_req->local_key;
+	WRITE_ONCE(msk->local_key, subflow_req->local_key);
 	msk->token = subflow_req->token;
 	msk->in_accept_queue = 1;
 	WRITE_ONCE(msk->fully_established, false);

net/mptcp/protocol.h

@@ -260,8 +260,10 @@ struct mptcp_data_frag {
 struct mptcp_sock {
 	/* inet_connection_sock must be the first member */
 	struct inet_connection_sock sk;
-	u64		local_key;
-	u64		remote_key;
+	u64		local_key;		/* protected by the first subflow socket lock
+						 * lockless access read
+						 */
+	u64		remote_key;		/* same as above */
 	u64		write_seq;
 	u64		bytes_sent;
 	u64		snd_nxt;

net/mptcp/subflow.c

@@ -75,7 +75,8 @@ static void subflow_req_create_thmac(struct mptcp_subflow_request_sock *subflow_
 
 	get_random_bytes(&subflow_req->local_nonce, sizeof(u32));
 
-	subflow_generate_hmac(msk->local_key, msk->remote_key,
+	subflow_generate_hmac(READ_ONCE(msk->local_key),
+			      READ_ONCE(msk->remote_key),
 			      subflow_req->local_nonce,
 			      subflow_req->remote_nonce, hmac);
 
@@ -694,7 +695,8 @@ static bool subflow_hmac_valid(const struct request_sock *req,
 	if (!msk)
 		return false;
 
-	subflow_generate_hmac(msk->remote_key, msk->local_key,
+	subflow_generate_hmac(READ_ONCE(msk->remote_key),
+			      READ_ONCE(msk->local_key),
 			      subflow_req->remote_nonce,
 			      subflow_req->local_nonce, hmac);
 
@@ -1530,8 +1532,8 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
 	mptcp_pm_get_flags_and_ifindex_by_id(msk, local_id,
 					     &flags, &ifindex);
 	subflow->remote_key_valid = 1;
-	subflow->remote_key = msk->remote_key;
-	subflow->local_key = msk->local_key;
+	subflow->remote_key = READ_ONCE(msk->remote_key);
+	subflow->local_key = READ_ONCE(msk->local_key);
 	subflow->token = msk->token;
 	mptcp_info2sockaddr(loc, &addr, ssk->sk_family);