diff --git a/tools/testing/vsock/vsock_perf.c b/tools/testing/vsock/vsock_perf.c
index 22633c2848cc7d..8e0a6c0770d372 100644
--- a/tools/testing/vsock/vsock_perf.c
+++ b/tools/testing/vsock/vsock_perf.c
@@ -33,7 +33,7 @@
 
 static unsigned int port = DEFAULT_PORT;
 static unsigned long buf_size_bytes = DEFAULT_BUF_SIZE_BYTES;
-static unsigned long vsock_buf_bytes = DEFAULT_VSOCK_BUF_BYTES;
+static unsigned long long vsock_buf_bytes = DEFAULT_VSOCK_BUF_BYTES;
 static bool zerocopy;
 
 static void error(const char *s)
@@ -162,7 +162,7 @@ static void run_receiver(int rcvlowat_bytes)
 	printf("Run as receiver\n");
 	printf("Listen port %u\n", port);
 	printf("RX buffer %lu bytes\n", buf_size_bytes);
-	printf("vsock buffer %lu bytes\n", vsock_buf_bytes);
+	printf("vsock buffer %llu bytes\n", vsock_buf_bytes);
 	printf("SO_RCVLOWAT %d bytes\n", rcvlowat_bytes);
 
 	fd = socket(AF_VSOCK, SOCK_STREAM, 0);
diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index 7fd25b814b4b62..0b7f5bf546da56 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -429,7 +429,7 @@ static void test_seqpacket_msg_bounds_client(const struct test_opts *opts)
 
 static void test_seqpacket_msg_bounds_server(const struct test_opts *opts)
 {
-	unsigned long sock_buf_size;
+	unsigned long long sock_buf_size;
 	unsigned long remote_hash;
 	unsigned long curr_hash;
 	int fd;
@@ -634,7 +634,8 @@ static void test_seqpacket_timeout_server(const struct test_opts *opts)
 
 static void test_seqpacket_bigmsg_client(const struct test_opts *opts)
 {
-	unsigned long sock_buf_size;
+	unsigned long long sock_buf_size;
+	size_t buf_size;
 	socklen_t len;
 	void *data;
 	int fd;
@@ -655,13 +656,20 @@ static void test_seqpacket_bigmsg_client(const struct test_opts *opts)
 
 	sock_buf_size++;
 
-	data = malloc(sock_buf_size);
+	/* size_t can be < unsigned long long */
+	buf_size = (size_t)sock_buf_size;
+	if (buf_size != sock_buf_size) {
+		fprintf(stderr, "Returned BUFFER_SIZE too large\n");
+		exit(EXIT_FAILURE);
+	}
+
+	data = malloc(buf_size);
 	if (!data) {
 		perror("malloc");
 		exit(EXIT_FAILURE);
 	}
 
-	send_buf(fd, data, sock_buf_size, 0, -EMSGSIZE);
+	send_buf(fd, data, buf_size, 0, -EMSGSIZE);
 
 	control_writeln("CLISENT");
 
@@ -1360,6 +1368,7 @@ static void test_stream_credit_update_test(const struct test_opts *opts,
 	int recv_buf_size;
 	struct pollfd fds;
 	size_t buf_size;
+	unsigned long long sock_buf_size;
 	void *buf;
 	int fd;
 
@@ -1371,8 +1380,11 @@ static void test_stream_credit_update_test(const struct test_opts *opts,
 
 	buf_size = RCVLOWAT_CREDIT_UPD_BUF_SIZE;
 
+	/* size_t can be < unsigned long long */
+	sock_buf_size = buf_size;
+
 	if (setsockopt(fd, AF_VSOCK, SO_VM_SOCKETS_BUFFER_SIZE,
-		       &buf_size, sizeof(buf_size))) {
+		       &sock_buf_size, sizeof(sock_buf_size))) {
 		perror("setsockopt(SO_VM_SOCKETS_BUFFER_SIZE)");
 		exit(EXIT_FAILURE);
 	}