qga: fix leak of base64 decoded data on command error

If the guest command fails to be spawned, then we would leak the decoded
base64 input used for the command's stdin feed.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>

qga/commands.c

@@ -402,7 +402,7 @@ GuestExec *qmp_guest_exec(const char *path,
     GIOChannel *in_ch, *out_ch, *err_ch;
     GSpawnFlags flags;
     bool has_output = (has_capture_output && capture_output);
-    uint8_t *input = NULL;
+    g_autofree uint8_t *input = NULL;
     size_t ninput = 0;
 
     arglist.value = (char *)path;
@@ -441,7 +441,7 @@ GuestExec *qmp_guest_exec(const char *path,
     g_child_watch_add(pid, guest_exec_child_watch, gei);
 
     if (has_input_data) {
-        gei->in.data = input;
+        gei->in.data = g_steal_pointer(&input);
         gei->in.size = ninput;
 #ifdef G_OS_WIN32
         in_ch = g_io_channel_win32_new_fd(in_fd);