qemu: monitor: Fix a memory leak in qemuMonitorJSONAttachCharDevCommand

With the current logic, we only free @tlsalias as part of the error
label and would have to free it explicitly earlier in the code. Convert
the error label to cleanup, so that we have only one sink, where we
handle all frees. Since JSON object append operation consumes pointers,
make sure @backend is cleared before we hit the cleanup label.
Signed-off-by: NErik Skultety <eskultet@redhat.com>
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>

src/qemu/qemu_monitor_json.c

@@ -6430,8 +6430,8 @@ static virJSONValuePtr
 qemuMonitorJSONAttachCharDevCommand(const char *chrID,
                                     const virDomainChrSourceDef *chr)
 {
-    virJSONValuePtr ret;
-    virJSONValuePtr backend;
+    virJSONValuePtr ret = NULL;
+    virJSONValuePtr backend = NULL;
     virJSONValuePtr data = NULL;
     virJSONValuePtr addr = NULL;
     const char *backend_type = NULL;
@@ -6440,7 +6440,7 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,
 
     if (!(backend = virJSONValueNewObject()) ||
         !(data = virJSONValueNewObject())) {
-        goto error;
+        goto cleanup;
     }
 
     switch ((virDomainChrType) chr->type) {
@@ -6456,14 +6456,14 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,
     case VIR_DOMAIN_CHR_TYPE_FILE:
         backend_type = "file";
         if (virJSONValueObjectAppendString(data, "out", chr->data.file.path) < 0)
-            goto error;
+            goto cleanup;
         break;
 
     case VIR_DOMAIN_CHR_TYPE_DEV:
         backend_type = STRPREFIX(chrID, "parallel") ? "parallel" : "serial";
         if (virJSONValueObjectAppendString(data, "device",
                                            chr->data.file.path) < 0)
-            goto error;
+            goto cleanup;
         break;
 
     case VIR_DOMAIN_CHR_TYPE_TCP:
@@ -6472,7 +6472,7 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,
                                                      chr->data.tcp.service);
         if (!addr ||
             virJSONValueObjectAppend(data, "addr", addr) < 0)
-            goto error;
+            goto cleanup;
         addr = NULL;
 
         telnet = chr->data.tcp.protocol == VIR_DOMAIN_CHR_TCP_PROTOCOL_TELNET;
@@ -6480,13 +6480,13 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,
         if (virJSONValueObjectAppendBoolean(data, "wait", false) < 0 ||
             virJSONValueObjectAppendBoolean(data, "telnet", telnet) < 0 ||
             virJSONValueObjectAppendBoolean(data, "server", chr->data.tcp.listen) < 0)
-            goto error;
+            goto cleanup;
         if (chr->data.tcp.tlscreds) {
             if (!(tlsalias = qemuAliasTLSObjFromSrcAlias(chrID)))
-                goto error;
+                goto cleanup;
 
             if (virJSONValueObjectAppendString(data, "tls-creds", tlsalias) < 0)
-                goto error;
+                goto cleanup;
         }
         break;
 
@@ -6496,14 +6496,14 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,
                                                      chr->data.udp.connectService);
         if (!addr ||
             virJSONValueObjectAppend(data, "remote", addr) < 0)
-            goto error;
+            goto cleanup;
 
         if (chr->data.udp.bindHost) {
             addr = qemuMonitorJSONBuildInetSocketAddress(chr->data.udp.bindHost,
                                                          chr->data.udp.bindService);
             if (!addr ||
                 virJSONValueObjectAppend(data, "local", addr) < 0)
-                goto error;
+                goto cleanup;
         }
         addr = NULL;
         break;
@@ -6514,12 +6514,12 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,
 
         if (!addr ||
             virJSONValueObjectAppend(data, "addr", addr) < 0)
-            goto error;
+            goto cleanup;
         addr = NULL;
 
         if (virJSONValueObjectAppendBoolean(data, "wait", false) < 0 ||
             virJSONValueObjectAppendBoolean(data, "server", chr->data.nix.listen) < 0)
-            goto error;
+            goto cleanup;
         break;
 
     case VIR_DOMAIN_CHR_TYPE_SPICEVMC:
@@ -6527,7 +6527,7 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,
 
         if (virJSONValueObjectAppendString(data, "type",
                                            virDomainChrSpicevmcTypeToString(chr->data.spicevmc)) < 0)
-            goto error;
+            goto cleanup;
         break;
 
     case VIR_DOMAIN_CHR_TYPE_SPICEPORT:
@@ -6544,28 +6544,27 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,
                            _("Hotplug unsupported for char device type '%d'"),
                            chr->type);
         }
-        goto error;
+        goto cleanup;
     }
 
     if (virJSONValueObjectAppendString(backend, "type", backend_type) < 0 ||
         virJSONValueObjectAppend(backend, "data", data) < 0)
-        goto error;
+        goto cleanup;
     data = NULL;
 
     if (!(ret = qemuMonitorJSONMakeCommand("chardev-add",
                                            "s:id", chrID,
                                            "a:backend", backend,
                                            NULL)))
-        goto error;
-
-    return ret;
+        goto cleanup;
+    backend = NULL;
 
- error:
+ cleanup:
     VIR_FREE(tlsalias);
     virJSONValueFree(addr);
     virJSONValueFree(data);
     virJSONValueFree(backend);
-    return NULL;
+    return ret;
 }