agp: zero pages before sending to userspace

AGP pages might be mapped into userspace finally, so the pages should be
set to zero before userspace can use it. Otherwise there is potential
information leakage.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/char/agp/generic.c

@@ -1226,7 +1226,7 @@ int agp_generic_alloc_pages(struct agp_bridge_data *bridge, struct agp_memory *m
 	int i, ret = -ENOMEM;
 
 	for (i = 0; i < num_pages; i++) {
-		page = alloc_page(GFP_KERNEL | GFP_DMA32);
+		page = alloc_page(GFP_KERNEL | GFP_DMA32 | __GFP_ZERO);
 		/* agp_free_memory() needs gart address */
 		if (page == NULL)
 			goto out;
@@ -1257,7 +1257,7 @@ void *agp_generic_alloc_page(struct agp_bridge_data *bridge)
 {
 	struct page * page;
 
-	page = alloc_page(GFP_KERNEL | GFP_DMA32);
+	page = alloc_page(GFP_KERNEL | GFP_DMA32 | __GFP_ZERO);
 	if (page == NULL)
 		return NULL;