On Tue, Apr 11, 2017 at 9:16 AM, Christoph Lameter <c...@linux.com> wrote: > On Tue, 11 Apr 2017, Michal Hocko wrote: > >> static inline void *index_to_obj(struct kmem_cache *cache, struct page >> *page, >> @@ -3813,14 +3818,18 @@ void kfree(const void *objp) >> { >> struct kmem_cache *c; >> unsigned long flags; >> + struct page *page; >> >> trace_kfree(_RET_IP_, objp); >> >> if (unlikely(ZERO_OR_NULL_PTR(objp))) >> return; >> + page = virt_to_head_page(obj); >> + if (CHECK_DATA_CORRUPTION(!PageSlab(page))) > > There is a flag SLAB_DEBUG_OBJECTS that is available for this check. > Consistency checks are configuraable in the slab allocator. > > Mentioned that before and got this lecture about data consistency checks.
It seems that enabling the debug checks comes with a non-trivial performance impact. I'd like to see consistency checks by default so we can handle intentional heap corruption attacks better. This check isn't expensive... -Kees -- Kees Cook Pixel Security