tests/migration: fix memleak in wait_command/wait_command_fd

Properly free each command resp to avoid memory leak.
ASAN shows memory leak stack:

Indirect leak of 2352520 byte(s) in 571 object(s) allocated from:
    #0 0x7f6ca3308d4e in __interceptor_calloc (/lib64/libasan.so.5+0x112d4e)
    #1 0x7f6ca3127a50 in g_malloc0 (/lib64/libglib-2.0.so.0+0x55a50)
    #2 0x557bf3c71d2b in qdict_new ../qobject/qdict.c:29
    #3 0x557bf3c9caba in parse_object ../qobject/json-parser.c:318
    #4 0x557bf3c9ce75 in json_parser_parse ../qobject/json-parser.c:580
    #5 0x557bf3c8c8cf in json_message_process_token ../qobject/json-streamer.c:92
    #6 0x557bf3c9ea59 in json_lexer_feed_char ../qobject/json-lexer.c:313
    #7 0x557bf3c9eeb5 in json_lexer_feed ../qobject/json-lexer.c:350
    #8 0x557bf3c4793a in qmp_fd_receive ../tests/qtest/libqtest.c:608
    #9 0x557bf3c47b58 in qtest_qmp_receive ../tests/qtest/libqtest.c:618
    #10 0x557bf3c44245 in wait_command ../tests/qtest/migration-helpers.c:59
    #11 0x557bf3c445cb in migrate_query_status ../tests/qtest/migration-helpers.c:108
    #12 0x557bf3c44642 in check_migration_status ../tests/qtest/migration-helpers.c:124
    #13 0x557bf3c447e7 in wait_for_migration_status ../tests/qtest/migration-helpers.c:148
    #14 0x557bf3c43b8f in test_migrate_auto_converge ../tests/qtest/migration-test.c:1243
    ......

Fix: 5e34005

Reported-by: Euler Robot <[email protected]>
Signed-off-by: Chen Qun <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Thomas Huth <[email protected]>

Author: Kuhn-Chen

tests/qtest/migration-helpers.c

@@ -32,7 +32,7 @@ static void check_stop_event(QTestState *who)
 QDict *wait_command_fd(QTestState *who, int fd, const char *command, ...)
 {
     va_list ap;
-    QDict *resp;
+    QDict *resp, *ret;
 
     va_start(ap, command);
     qtest_qmp_vsend_fds(who, &fd, 1, command, ap);
@@ -44,7 +44,11 @@ QDict *wait_command_fd(QTestState *who, int fd, const char *command, ...)
     g_assert(!qdict_haskey(resp, "error"));
     g_assert(qdict_haskey(resp, "return"));
 
-    return qdict_get_qdict(resp, "return");
+    ret = qdict_get_qdict(resp, "return");
+    qobject_ref(ret);
+    qobject_unref(resp);
+
+    return ret;
 }
 
 /*
@@ -53,7 +57,7 @@ QDict *wait_command_fd(QTestState *who, int fd, const char *command, ...)
 QDict *wait_command(QTestState *who, const char *command, ...)
 {
     va_list ap;
-    QDict *resp;
+    QDict *resp, *ret;
 
     va_start(ap, command);
     resp = qtest_vqmp(who, command, ap);
@@ -64,7 +68,11 @@ QDict *wait_command(QTestState *who, const char *command, ...)
     g_assert(!qdict_haskey(resp, "error"));
     g_assert(qdict_haskey(resp, "return"));
 
-    return qdict_get_qdict(resp, "return");
+    ret = qdict_get_qdict(resp, "return");
+    qobject_ref(ret);
+    qobject_unref(resp);
+
+    return ret;
 }
 
 /*