hw/display: fix memleak from virtio_add_resource

When the given uuid is already present in the hash table,
virtio_add_resource() does not add the passed VirtioSharedObject. In
this case, free it in the callers to avoid leaking memory. This fixed
the following `make check` error, when built with --enable-sanitizers:

  4/166 qemu:unit / test-virtio-dmabuf   ERROR 1.51s   exit status 1

  ==7716==ERROR: LeakSanitizer: detected memory leaks
  Direct leak of 320 byte(s) in 20 object(s) allocated from:
      #0 0x7f6fc16e3808 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cc:144
      #1 0x7f6fc1503e98 in g_malloc (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x57e98)
      #2 0x564d63cafb6b in test_add_invalid_resource ../tests/unit/test-virtio-dmabuf.c:100
      #3 0x7f6fc152659d  (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x7a59d)
  SUMMARY: AddressSanitizer: 320 byte(s) leaked in 20 allocation(s).

The changes at virtio_add_resource() itself are not strictly necessary
for the memleak fix, but they make it more obvious that, on an error
return, the passed object is not added to the hash.

Signed-off-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Message-Id: <c61c13f9a0c67dec473bdbfc8789c29ef26c900b.1696624734.git.quic_mathbern@quicinc.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Albert Esteve <aesteve@redhat.com>
Signed-off-by: Matheus Tavares Bernardino &lt;<a href="mailto:quic_mathbern@quicinc.com" target="_blank">quic_mathbern@quicinc.com</a>&gt;<br>

hw/display/virtio-dmabuf.c

@@ -29,7 +29,7 @@ static int uuid_equal_func(const void *lhv, const void *rhv)
 
 static bool virtio_add_resource(QemuUUID *uuid, VirtioSharedObject *value)
 {
-    bool result = false;
+    bool result = true;
 
     g_mutex_lock(&lock);
     if (resource_uuids == NULL) {
@@ -39,7 +39,9 @@ static bool virtio_add_resource(QemuUUID *uuid, VirtioSharedObject *value)
                                                g_free);
     }
     if (g_hash_table_lookup(resource_uuids, uuid) == NULL) {
-        result = g_hash_table_insert(resource_uuids, uuid, value);
+        g_hash_table_insert(resource_uuids, uuid, value);
+    } else {
+        result = false;
     }
     g_mutex_unlock(&lock);
 
@@ -57,6 +59,9 @@ bool virtio_add_dmabuf(QemuUUID *uuid, int udmabuf_fd)
     vso->type = TYPE_DMABUF;
     vso->value = GINT_TO_POINTER(udmabuf_fd);
     result = virtio_add_resource(uuid, vso);
+    if (!result) {
+        g_free(vso);
+    }
 
     return result;
 }
@@ -72,6 +77,9 @@ bool virtio_add_vhost_device(QemuUUID *uuid, struct vhost_dev *dev)
     vso->type = TYPE_VHOST_DEV;
     vso->value = dev;
     result = virtio_add_resource(uuid, vso);
+    if (!result) {
+        g_free(vso);
+    }
 
     return result;
 }