mptcp: don't return sockets in foreign netns

mptcp_token_get_sock() may return a mptcp socket that is in
a different net namespace than the socket that received the token value.

The mptcp syncookie code path had an explicit check for this,
this moves the test into mptcp_token_get_sock() function.

Eventually token.c should be converted to pernet storage, but
such change is not suitable for net tree.

Fixes: 2c5ebd00 ("mptcp: refactor token container")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/mptcp_diag.c

@@ -36,7 +36,7 @@ static int mptcp_diag_dump_one(struct netlink_callback *cb,
 	struct sock *sk;
 
 	net = sock_net(in_skb->sk);
-	msk = mptcp_token_get_sock(req->id.idiag_cookie[0]);
+	msk = mptcp_token_get_sock(net, req->id.idiag_cookie[0]);
 	if (!msk)
 		goto out_nosk;
 

net/mptcp/protocol.h

@@ -709,7 +709,7 @@ int mptcp_token_new_connect(struct sock *sk);
 void mptcp_token_accept(struct mptcp_subflow_request_sock *r,
 			struct mptcp_sock *msk);
 bool mptcp_token_exists(u32 token);
-struct mptcp_sock *mptcp_token_get_sock(u32 token);
+struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token);
 struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
 					 long *s_num);
 void mptcp_token_destroy(struct mptcp_sock *msk);

net/mptcp/subflow.c

@@ -86,7 +86,7 @@ static struct mptcp_sock *subflow_token_join_request(struct request_sock *req)
 	struct mptcp_sock *msk;
 	int local_id;
 
-	msk = mptcp_token_get_sock(subflow_req->token);
+	msk = mptcp_token_get_sock(sock_net(req_to_sk(req)), subflow_req->token);
 	if (!msk) {
 		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINNOTOKEN);
 		return NULL;

net/mptcp/syncookies.c

@@ -108,18 +108,12 @@ bool mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subfl
 
 	e->valid = 0;
 
-	msk = mptcp_token_get_sock(e->token);
+	msk = mptcp_token_get_sock(net, e->token);
 	if (!msk) {
 		spin_unlock_bh(&join_entry_locks[i]);
 		return false;
 	}
 
-	/* If this fails, the token got re-used in the mean time by another
-	 * mptcp socket in a different netns, i.e. entry is outdated.
-	 */
-	if (!net_eq(sock_net((struct sock *)msk), net))
-		goto err_put;
-
 	subflow_req->remote_nonce = e->remote_nonce;
 	subflow_req->local_nonce = e->local_nonce;
 	subflow_req->backup = e->backup;
@@ -128,11 +122,6 @@ bool mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subfl
 	subflow_req->msk = msk;
 	spin_unlock_bh(&join_entry_locks[i]);
 	return true;
-
-err_put:
-	spin_unlock_bh(&join_entry_locks[i]);
-	sock_put((struct sock *)msk);
-	return false;
 }
 
 void __init mptcp_join_cookie_init(void)

net/mptcp/token.c

@@ -231,6 +231,7 @@ bool mptcp_token_exists(u32 token)
 
 /**
  * mptcp_token_get_sock - retrieve mptcp connection sock using its token
+ * @net: restrict to this namespace
  * @token: token of the mptcp connection to retrieve
  *
  * This function returns the mptcp connection structure with the given token.
@@ -238,7 +239,7 @@ bool mptcp_token_exists(u32 token)
  *
  * returns NULL if no connection with the given token value exists.
  */
-struct mptcp_sock *mptcp_token_get_sock(u32 token)
+struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token)
 {
 	struct hlist_nulls_node *pos;
 	struct token_bucket *bucket;
@@ -251,11 +252,15 @@ struct mptcp_sock *mptcp_token_get_sock(u32 token)
 again:
 	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
 		msk = mptcp_sk(sk);
-		if (READ_ONCE(msk->token) != token)
+		if (READ_ONCE(msk->token) != token ||
+		    !net_eq(sock_net(sk), net))
 			continue;
+
 		if (!refcount_inc_not_zero(&sk->sk_refcnt))
 			goto not_found;
-		if (READ_ONCE(msk->token) != token) {
+
+		if (READ_ONCE(msk->token) != token ||
+		    !net_eq(sock_net(sk), net)) {
 			sock_put(sk);
 			goto again;
 		}

net/mptcp/token_test.c

@@ -11,6 +11,7 @@ static struct mptcp_subflow_request_sock *build_req_sock(struct kunit *test)
 			    GFP_USER);
 	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, req);
 	mptcp_token_init_request((struct request_sock *)req);
+	sock_net_set((struct sock *)req, &init_net);
 	return req;
 }
 
@@ -22,7 +23,7 @@ static void mptcp_token_test_req_basic(struct kunit *test)
 	KUNIT_ASSERT_EQ(test, 0,
 			mptcp_token_new_request((struct request_sock *)req));
 	KUNIT_EXPECT_NE(test, 0, (int)req->token);
-	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(req->token));
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(&init_net, req->token));
 
 	/* cleanup */
 	mptcp_token_destroy_request((struct request_sock *)req);
@@ -55,6 +56,7 @@ static struct mptcp_sock *build_msk(struct kunit *test)
 	msk = kunit_kzalloc(test, sizeof(struct mptcp_sock), GFP_USER);
 	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, msk);
 	refcount_set(&((struct sock *)msk)->sk_refcnt, 1);
+	sock_net_set((struct sock *)msk, &init_net);
 	return msk;
 }
 
@@ -74,11 +76,11 @@ static void mptcp_token_test_msk_basic(struct kunit *test)
 			mptcp_token_new_connect((struct sock *)icsk));
 	KUNIT_EXPECT_NE(test, 0, (int)ctx->token);
 	KUNIT_EXPECT_EQ(test, ctx->token, msk->token);
-	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(ctx->token));
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, ctx->token));
 	KUNIT_EXPECT_EQ(test, 2, (int)refcount_read(&sk->sk_refcnt));
 
 	mptcp_token_destroy(msk);
-	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(ctx->token));
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(&init_net, ctx->token));
 }
 
 static void mptcp_token_test_accept(struct kunit *test)
@@ -90,11 +92,11 @@ static void mptcp_token_test_accept(struct kunit *test)
 			mptcp_token_new_request((struct request_sock *)req));
 	msk->token = req->token;
 	mptcp_token_accept(req, msk);
-	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(msk->token));
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, msk->token));
 
 	/* this is now a no-op */
 	mptcp_token_destroy_request((struct request_sock *)req);
-	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(msk->token));
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, msk->token));
 
 	/* cleanup */
 	mptcp_token_destroy(msk);
@@ -116,7 +118,7 @@ static void mptcp_token_test_destroyed(struct kunit *test)
 
 	/* simulate race on removal */
 	refcount_set(&sk->sk_refcnt, 0);
-	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(msk->token));
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(&init_net, msk->token));
 
 	/* cleanup */
 	mptcp_token_destroy(msk);