vsock/test: Add test for sk_error_queue memory leak

Ask for MSG_ZEROCOPY completion notification, but do not recv() it.
Test attempts to create a memory leak, kmemleak should be employed.

Fixed by commit fbf7085b3a ("vsock: Fix sk_error_queue memory leak").

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Link: https://patch.msgid.link/20241219-test-vsock-leaks-v4-6-a416e554d9d7@rbox.co
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/vsock/vsock_test.c

@@ -1521,6 +1521,46 @@ static void test_stream_leak_acceptq_server(const struct test_opts *opts)
 	}
 }
 
+/* Test for a memory leak. User is expected to run kmemleak scan, see README. */
+static void test_stream_msgzcopy_leak_errq_client(const struct test_opts *opts)
+{
+	struct pollfd fds = { 0 };
+	int fd;
+
+	fd = vsock_stream_connect(opts->peer_cid, opts->peer_port);
+	if (fd < 0) {
+		perror("connect");
+		exit(EXIT_FAILURE);
+	}
+
+	enable_so_zerocopy_check(fd);
+	send_byte(fd, 1, MSG_ZEROCOPY);
+
+	fds.fd = fd;
+	fds.events = 0;
+	if (poll(&fds, 1, -1) < 0) {
+		perror("poll");
+		exit(EXIT_FAILURE);
+	}
+
+	close(fd);
+}
+
+static void test_stream_msgzcopy_leak_errq_server(const struct test_opts *opts)
+{
+	int fd;
+
+	fd = vsock_stream_accept(VMADDR_CID_ANY, opts->peer_port, NULL);
+	if (fd < 0) {
+		perror("accept");
+		exit(EXIT_FAILURE);
+	}
+
+	recv_byte(fd, 1, 0);
+	vsock_wait_remote_close(fd);
+	close(fd);
+}
+
 static struct test_case test_cases[] = {
 	{
 		.name = "SOCK_STREAM connection reset",
@@ -1656,6 +1696,11 @@ static struct test_case test_cases[] = {
 		.run_client = test_stream_leak_acceptq_client,
 		.run_server = test_stream_leak_acceptq_server,
 	},
+	{
+		.name = "SOCK_STREAM MSG_ZEROCOPY leak MSG_ERRQUEUE",
+		.run_client = test_stream_msgzcopy_leak_errq_client,
+		.run_server = test_stream_msgzcopy_leak_errq_server,
+	},
 	{},
 };