libqtest: escape strings in QMP commands, fix leak

libqtest is using g_strdup_printf to format QMP commands, but
this does not work if the argument strings need to be escaped.
Instead, use the fancy %-formatting functionality of QObject.
The only change required in tests is that strings have to be
formatted as %s, not '%s' or \"%s\".  Luckily this usage of
parameterized QMP commands is not that frequent.

The leak is in socket_sendf.  Since we are extracting the send
loop to a new function, fix it now.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tests/fdc-test.c

@@ -291,7 +291,7 @@ static void test_media_insert(void)
     /* Insert media in drive. DSKCHK should not be reset until a step pulse
      * is sent. */
     qmp_discard_response("{'execute':'change', 'arguments':{"
-                         " 'device':'floppy0', 'target': '%s' }}",
+                         " 'device':'floppy0', 'target': %s }}",
                          test_image);
     qmp_discard_response(""); /* ignore event
                                  (FIXME open -> open transition?!) */

tests/libqtest.c

@@ -30,8 +30,9 @@
 
 #include "qemu/compiler.h"
 #include "qemu/osdep.h"
-#include "qapi/qmp/json-streamer.h"
 #include "qapi/qmp/json-parser.h"
+#include "qapi/qmp/json-streamer.h"
+#include "qapi/qmp/qjson.h"
 
 #define MAX_IRQ 256
 #define SOCKET_TIMEOUT 5
@@ -220,19 +221,15 @@ void qtest_quit(QTestState *s)
     g_free(s);
 }
 
-static void socket_sendf(int fd, const char *fmt, va_list ap)
+static void socket_send(int fd, const char *buf, size_t size)
 {
-    gchar *str;
-    size_t size, offset;
-
-    str = g_strdup_vprintf(fmt, ap);
-    size = strlen(str);
+    size_t offset;
 
     offset = 0;
     while (offset < size) {
         ssize_t len;
 
-        len = write(fd, str + offset, size - offset);
+        len = write(fd, buf + offset, size - offset);
         if (len == -1 && errno == EINTR) {
             continue;
         }
@@ -244,6 +241,15 @@ static void socket_sendf(int fd, const char *fmt, va_list ap)
     }
 }
 
+static void socket_sendf(int fd, const char *fmt, va_list ap)
+{
+    gchar *str = g_strdup_vprintf(fmt, ap);
+    size_t size = strlen(str);
+
+    socket_send(fd, str, size);
+    g_free(str);
+}
+
 static void GCC_FMT_ATTR(2, 3) qtest_sendf(QTestState *s, const char *fmt, ...)
 {
     va_list ap;
@@ -378,8 +384,29 @@ QDict *qtest_qmp_receive(QTestState *s)
 
 QDict *qtest_qmpv(QTestState *s, const char *fmt, va_list ap)
 {
+    va_list ap_copy;
+    QObject *qobj;
+
+    /* Going through qobject ensures we escape strings properly.
+     * This seemingly unnecessary copy is required in case va_list
+     * is an array type.
+     */
+    va_copy(ap_copy, ap);
+    qobj = qobject_from_jsonv(fmt, &ap_copy);
+    va_end(ap_copy);
+
+    /* No need to send anything for an empty QObject.  */
+    if (qobj) {
+        QString *qstr = qobject_to_json(qobj);
+        const char *str = qstring_get_str(qstr);
+        size_t size = qstring_get_length(qstr);
+
         /* Send QMP request */
-    socket_sendf(s->qmp_fd, fmt, ap);
+        socket_send(s->qmp_fd, str, size);
+
+        QDECREF(qstr);
+        qobject_decref(qobj);
+    }
 
     /* Receive reply */
     return qtest_qmp_receive(s);

tests/qom-test.c

@@ -53,7 +53,7 @@ static void test_properties(const char *path, bool recurse)
 
     g_test_message("Obtaining properties of %s", path);
     response = qmp("{ 'execute': 'qom-list',"
-                   "  'arguments': { 'path': '%s' } }", path);
+                   "  'arguments': { 'path': %s } }", path);
     g_assert(response);
 
     if (!recurse) {
@@ -76,8 +76,8 @@ static void test_properties(const char *path, bool recurse)
             const char *prop = qdict_get_str(tuple, "name");
             g_test_message("Testing property %s.%s", path, prop);
             response = qmp("{ 'execute': 'qom-get',"
-                           "  'arguments': { 'path': '%s',"
-                           "                 'property': '%s' } }",
+                           "  'arguments': { 'path': %s,"
+                           "                 'property': %s } }",
                            path, prop);
             /* qom-get may fail but should not, e.g., segfault. */
             g_assert(response);

tests/tmp105-test.c

@@ -69,7 +69,7 @@ static int qmp_tmp105_get_temperature(const char *id)
     QDict *response;
     int ret;
 
-    response = qmp("{ 'execute': 'qom-get', 'arguments': { 'path': '%s', "
+    response = qmp("{ 'execute': 'qom-get', 'arguments': { 'path': %s, "
                    "'property': 'temperature' } }", id);
     g_assert(qdict_haskey(response, "return"));
     ret = qdict_get_int(response, "return");
@@ -81,7 +81,7 @@ static void qmp_tmp105_set_temperature(const char *id, int value)
 {
     QDict *response;
 
-    response = qmp("{ 'execute': 'qom-set', 'arguments': { 'path': '%s', "
+    response = qmp("{ 'execute': 'qom-set', 'arguments': { 'path': %s, "
                    "'property': 'temperature', 'value': %d } }", id, value);
     g_assert(qdict_haskey(response, "return"));
     QDECREF(response);