[KMS/DRM] Fix for bug #5468: corruption on dynamic cursor changing caused by wrong buffer size.

src/video/kmsdrm/SDL_kmsdrmmouse.c

@@ -242,17 +242,15 @@ KMSDRM_ShowCursor(SDL_Cursor * cursor)
     /* Prepare a buffer we can dump to our GBM BO (different
        size, alpha premultiplication...) */
     bo_stride = KMSDRM_gbm_bo_get_stride(dispdata->cursor_bo);
-    bufsize = bo_stride * curdata->h;
+    bufsize = bo_stride * dispdata->cursor_h;
+
+    ready_buffer = (uint32_t*)SDL_calloc(1, bufsize);
 
-    ready_buffer = (uint32_t*)SDL_malloc(bufsize);
     if (!ready_buffer) {
         ret = SDL_OutOfMemory();
         goto cleanup;
     }
 
-    /* Clean the whole buffer we are preparing. */
-    SDL_memset(ready_buffer, 0x00, bo_stride * curdata->h);
-
     /* Copy from the cursor buffer to a buffer that we can dump to the GBM BO,
        pre-multiplying by alpha each pixel as we go. */
     for (i = 0; i < curdata->h; i++) {