vnc: add magic cookie to VncState

Set magic cookie on initialization.  Clear on cleanup.  Sprinkle a bunch
of assert()s checking the cookie, to verify the pointer is valid.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20180507102254.12107-1-kraxel@redhat.com

ui/vnc-jobs.c

@@ -82,6 +82,7 @@ VncJob *vnc_job_new(VncState *vs)
 {
     VncJob *job = g_new0(VncJob, 1);
 
+    assert(vs->magic == VNC_MAGIC);
     job->vs = vs;
     vnc_lock_queue(queue);
     QLIST_INIT(&job->rectangles);
@@ -214,6 +215,7 @@ static int vnc_worker_thread_loop(VncJobQueue *queue)
     /* Here job can only be NULL if queue->exit is true */
     job = QTAILQ_FIRST(&queue->jobs);
     vnc_unlock_queue(queue);
+    assert(job->vs->magic == VNC_MAGIC);
 
     if (queue->exit) {
         return -1;
@@ -236,6 +238,7 @@ static int vnc_worker_thread_loop(VncJobQueue *queue)
 
     /* Make a local copy of vs and switch output buffers */
     vnc_async_encoding_start(job->vs, &vs);
+    vs.magic = VNC_MAGIC;
 
     /* Start sending rectangles */
     n_rectangles = 0;
@@ -289,6 +292,7 @@ disconnected:
     vnc_unlock_queue(queue);
     qemu_cond_broadcast(&queue->cond);
     g_free(job);
+    vs.magic = 0;
     return 0;
 }
 

ui/vnc.c

@@ -1138,6 +1138,7 @@ static void audio_capture_notify(void *opaque, audcnotification_e cmd)
 {
     VncState *vs = opaque;
 
+    assert(vs->magic == VNC_MAGIC);
     switch (cmd) {
     case AUD_CNOTIFY_DISABLE:
         vnc_lock_output(vs);
@@ -1167,6 +1168,7 @@ static void audio_capture(void *opaque, void *buf, int size)
 {
     VncState *vs = opaque;
 
+    assert(vs->magic == VNC_MAGIC);
     vnc_lock_output(vs);
     if (vs->output.offset < vs->throttle_output_offset) {
         vnc_write_u8(vs, VNC_MSG_SERVER_QEMU);
@@ -1275,6 +1277,7 @@ void vnc_disconnect_finish(VncState *vs)
     vs->ioc = NULL;
     object_unref(OBJECT(vs->sioc));
     vs->sioc = NULL;
+    vs->magic = 0;
     g_free(vs);
 }
 
@@ -1414,7 +1417,7 @@ static void vnc_client_write_locked(VncState *vs)
 
 static void vnc_client_write(VncState *vs)
 {
-
+    assert(vs->magic == VNC_MAGIC);
     vnc_lock_output(vs);
     if (vs->output.offset) {
         vnc_client_write_locked(vs);
@@ -1487,6 +1490,7 @@ static void vnc_jobs_bh(void *opaque)
 {
     VncState *vs = opaque;
 
+    assert(vs->magic == VNC_MAGIC);
     vnc_jobs_consume_buffer(vs);
 }
 
@@ -1537,6 +1541,8 @@ gboolean vnc_client_io(QIOChannel *ioc G_GNUC_UNUSED,
                        GIOCondition condition, void *opaque)
 {
     VncState *vs = opaque;
+
+    assert(vs->magic == VNC_MAGIC);
     if (condition & G_IO_IN) {
         if (vnc_client_read(vs) < 0) {
             /* vs is free()ed here */
@@ -1568,6 +1574,7 @@ gboolean vnc_client_io(QIOChannel *ioc G_GNUC_UNUSED,
 
 void vnc_write(VncState *vs, const void *data, size_t len)
 {
+    assert(vs->magic == VNC_MAGIC);
     if (vs->disconnecting) {
         return;
     }
@@ -3064,6 +3071,7 @@ static void vnc_connect(VncDisplay *vd, QIOChannelSocket *sioc,
     int i;
 
     trace_vnc_client_connect(vs, sioc);
+    vs->magic = VNC_MAGIC;
     vs->sioc = sioc;
     object_ref(OBJECT(vs->sioc));
     vs->ioc = QIO_CHANNEL(sioc);

ui/vnc.h

@@ -255,8 +255,11 @@ typedef enum {
     VNC_STATE_UPDATE_FORCE,
 } VncStateUpdate;
 
+#define VNC_MAGIC ((uint64_t)0x05b3f069b3d204bb)
+
 struct VncState
 {
+    uint64_t magic;
     QIOChannelSocket *sioc; /* The underlying socket */
     QIOChannel *ioc; /* The channel currently used for I/O */
     guint ioc_tag;