Security fix. Zero pages before they are handed to user space.

TTM pages were not cleared when allocated and handed to user space.
Sensitive information may leak.

linux-core/drm_compat.c

@@ -259,6 +259,8 @@ struct page *drm_vm_ttm_nopage(struct vm_area_struct *vma,
 		}
 		++bm->cur_pages;
 		SetPageLocked(page);
+		clear_page(kmap(page));
+		kunmap(page);
 	}
 
 	get_page(page);

linux-core/drm_ttm.c

@@ -235,6 +235,8 @@ static int drm_ttm_populate(drm_ttm_t * ttm)
 #else
 			SetPageReserved(page);
 #endif
+			clear_page(kmap(page));
+			kunmap(page);
 			ttm->pages[i] = page;
 			++bm->cur_pages;
 		}

linux-core/drm_vm.c

@@ -220,6 +220,8 @@ struct page *drm_vm_ttm_fault(struct vm_area_struct *vma,
 #else
 		SetPageReserved(page);
 #endif
+		clear_page(kmap(page));
+		kunmap(page);
 	}
 
 	if (ttm->page_flags & DRM_TTM_PAGE_UNCACHED) {