[PATCH 1/9] mm: Hardened usercopy

On Thu, Jul 7, 2016 at 1:37 AM, Baruch Siach [off-list ref] wrote:

Hi Kees,

On Wed, Jul 06, 2016 at 03:25:20PM -0700, Kees Cook wrote:

quoted

+#ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR

Should be CONFIG_HARDENED_USERCOPY to match the slab/slub implementation
condition.

quoted

+const char *__check_heap_object(const void *ptr, unsigned long n,
+                             struct page *page);
+#else
+static inline const char *__check_heap_object(const void *ptr,
+                                           unsigned long n,
+                                           struct page *page)
+{
+     return NULL;
+}
+#endif

Hmm, I think what I have is correct: if the allocator supports the
heap object checking, it defines __check_heap_object as existing via
CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR. If usercopy checking is done
at all is controlled by CONFIG_HARDENED_USERCOPY.

I.e. you can have the other usercopy checks even if your allocator
doesn't support object size checking.

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security