From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f69.google.com (mail-it0-f69.google.com [209.85.214.69]) by kanga.kvack.org (Postfix) with ESMTP id 89BCB8E0001 for ; Wed, 12 Sep 2018 12:36:30 -0400 (EDT) Received: by mail-it0-f69.google.com with SMTP id w68-v6so4377771ith.0 for ; Wed, 12 Sep 2018 09:36:30 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id c65-v6sor1174020itc.93.2018.09.12.09.36.29 for (Google Transport Security); Wed, 12 Sep 2018 09:36:29 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <95b5beb7ec13b7e998efe84c9a7a5c1fa49a9fe3.1535462971.git.andreyknvl@google.com> References: <95b5beb7ec13b7e998efe84c9a7a5c1fa49a9fe3.1535462971.git.andreyknvl@google.com> From: Dmitry Vyukov Date: Wed, 12 Sep 2018 18:36:08 +0200 Message-ID: Subject: Re: [PATCH v6 08/18] khwasan: preassign tags to objects with ctors or SLAB_TYPESAFE_BY_RCU Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Konovalov Cc: Andrey Ryabinin , Alexander Potapenko , Catalin Marinas , Will Deacon , Christoph Lameter , Andrew Morton , Mark Rutland , Nick Desaulniers , Marc Zyngier , Dave Martin , Ard Biesheuvel , "Eric W . Biederman" , Ingo Molnar , Paul Lawrence , Geert Uytterhoeven , Arnd Bergmann , "Kirill A . Shutemov" , Greg Kroah-Hartman , Kate Stewart , Mike Rapoport , kasan-dev , linux-doc@vger.kernel.org, LKML , Linux ARM , linux-sparse@vger.kernel.org, Linux-MM , "open list:KERNEL BUILD + fi..." , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Jann Horn , Mark Brand , Chintan Pandya , Vishwath Mohan On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov wrote: > An object constructor can initialize pointers within this objects based on > the address of the object. Since the object address might be tagged, we > need to assign a tag before calling constructor. > > The implemented approach is to assign tags to objects with constructors > when a slab is allocated and call constructors once as usual. The > downside is that such object would always have the same tag when it is > reallocated, so we won't catch use-after-frees on it. > > Also pressign tags for objects from SLAB_TYPESAFE_BY_RCU caches, since > they can be validy accessed after having been freed. > > Signed-off-by: Andrey Konovalov > --- > mm/slab.c | 6 +++++- > mm/slub.c | 4 ++++ > 2 files changed, 9 insertions(+), 1 deletion(-) > > diff --git a/mm/slab.c b/mm/slab.c > index 6fdca9ec2ea4..3b4227059f2e 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -403,7 +403,11 @@ static inline struct kmem_cache *virt_to_cache(const void *obj) > static inline void *index_to_obj(struct kmem_cache *cache, struct page *page, > unsigned int idx) > { > - return page->s_mem + cache->size * idx; > + void *obj; > + > + obj = page->s_mem + cache->size * idx; > + obj = khwasan_preset_slab_tag(cache, idx, obj); > + return obj; > } > > /* > diff --git a/mm/slub.c b/mm/slub.c > index 4206e1b616e7..086d6558a6b6 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1531,12 +1531,14 @@ static bool shuffle_freelist(struct kmem_cache *s, struct page *page) > /* First entry is used as the base of the freelist */ > cur = next_freelist_entry(s, page, &pos, start, page_limit, > freelist_count); > + cur = khwasan_preset_slub_tag(s, cur); > page->freelist = cur; > > for (idx = 1; idx < page->objects; idx++) { > setup_object(s, page, cur); > next = next_freelist_entry(s, page, &pos, start, page_limit, > freelist_count); > + next = khwasan_preset_slub_tag(s, next); > set_freepointer(s, cur, next); > cur = next; > } > @@ -1613,8 +1615,10 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) > shuffle = shuffle_freelist(s, page); > > if (!shuffle) { > + start = khwasan_preset_slub_tag(s, start); > for_each_object_idx(p, idx, s, start, page->objects) { > setup_object(s, page, p); > + p = khwasan_preset_slub_tag(s, p); As I commented in the previous patch, can't we do this in kasan_init_slab_obj(), which should be called in all the right places already? > if (likely(idx < page->objects)) > set_freepointer(s, p, p + s->size); > else > -- > 2.19.0.rc0.228.g281dcd1b4d0-goog >