[PATCH] qemu: monitor: Fix a memory leak in qemuMonitorJSONAttachCharDevCommand

[Erik Skultety <eskultet@xxxxxxxxxx>]

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. In order to do that we need to clear some JSON obj
pointers down the success road to avoid SIGSEGV, since JSON object
append operation consumes pointers.

Signed-off-by: Erik Skultety <eskultet@xxxxxxxxxx>
---
 src/qemu/qemu_monitor_json.c | 47 ++++++++++++++++++++++----------------------
 1 file changed, 23 insertions(+), 24 deletions(-)

diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index f208dd05a..b8b73926f 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/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:
@@ -6472,21 +6472,20 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,
                                                      chr->data.tcp.service);
         if (!addr ||
             virJSONValueObjectAppend(data, "addr", addr) < 0)
-            goto error;
-        addr = NULL;
+            goto cleanup;

         telnet = chr->data.tcp.protocol == VIR_DOMAIN_CHR_TCP_PROTOCOL_TELNET;

         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;

@@ -6496,16 +6495,15 @@ 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;

     case VIR_DOMAIN_CHR_TYPE_UNIX:
@@ -6514,12 +6512,11 @@ qemuMonitorJSONAttachCharDevCommand(const char *chrID,

         if (!addr ||
             virJSONValueObjectAppend(data, "addr", addr) < 0)
-            goto error;
-        addr = NULL;
+            goto cleanup;

         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 +6524,7 @@ 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 +6541,30 @@ 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;
-    data = NULL;
+        goto cleanup;

     if (!(ret = qemuMonitorJSONMakeCommand("chardev-add",
                                            "s:id", chrID,
                                            "a:backend", backend,
                                            NULL)))
-        goto error;
+        goto cleanup;

-    return ret;
+    /* we must not free the following pointers as they've been collectively
+     * consumed by @ret, so clear them first
+     */
+    addr = data = backend = NULL;

- error:
+ cleanup:
     VIR_FREE(tlsalias);
     virJSONValueFree(addr);
     virJSONValueFree(data);
     virJSONValueFree(backend);
-    return NULL;
+    return ret;
 }


--
2.13.1

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