diff --git a/hw/dmx/dmx_glxvisuals.c b/hw/dmx/dmx_glxvisuals.c
index 027557add..56bd67b6e 100644
--- a/hw/dmx/dmx_glxvisuals.c
+++ b/hw/dmx/dmx_glxvisuals.c
@@ -279,7 +279,10 @@ GetGLXFBConfigs(Display * dpy, int glxMajorOpcode, int *nconfigs)
         return NULL;
     }
 
-    attrs = (INT32 *) Xmalloc(2 * numAttribs * __GLX_SIZE_CARD32);
+    if (numAttribs < (INT_MAX / (2 * __GLX_SIZE_CARD32)))
+        attrs = Xmalloc(2 * numAttribs * __GLX_SIZE_CARD32);
+    else
+        attrs = NULL;
     if (!attrs) {
         UnlockDisplay(dpy);
         SyncHandle();
@@ -287,15 +290,16 @@ GetGLXFBConfigs(Display * dpy, int glxMajorOpcode, int *nconfigs)
     }
 
     /* Allocate memory for our config structure */
-    config = (__GLXFBConfig *)
-        Xmalloc(numFBConfigs * sizeof(__GLXFBConfig));
+    if (numFBConfigs < (INT_MAX / sizeof(__GLXFBConfig)))
+        config = Xcalloc(numFBConfigs, sizeof(__GLXFBConfig));
+    else
+        config = NULL;
     if (!config) {
         free(attrs);
         UnlockDisplay(dpy);
         SyncHandle();
         return NULL;
     }
-    memset(config, 0, numFBConfigs * sizeof(__GLXFBConfig));
     fbconfigs = config;
 
     /* Convert attribute list into our format */