Re: [PATCH v2 03/21] KASAN: remove code paths guarded by CONFIG_SLAB

[Hyeonggon Yoo]

On Tue, Dec 5, 2023 at 1:27 PM Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> wrote:
>
> On Mon, Nov 20, 2023 at 07:34:14PM +0100, Vlastimil Babka wrote:
> > With SLAB removed and SLUB the only remaining allocator, we can clean up
> > some code that was depending on the choice.
> >
> > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
> > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> > ---
> >  mm/kasan/common.c     | 13 ++-----------
> >  mm/kasan/kasan.h      |  3 +--
> >  mm/kasan/quarantine.c |  7 -------
> >  3 files changed, 3 insertions(+), 20 deletions(-)
> >
> > diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> > index 256930da578a..5d95219e69d7 100644
> > --- a/mm/kasan/common.c
> > +++ b/mm/kasan/common.c
> > @@ -153,10 +153,6 @@ void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
> >   * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
> >   *    accessed after being freed. We preassign tags for objects in these
> >   *    caches as well.
> > - * 3. For SLAB allocator we can't preassign tags randomly since the freelist
> > - *    is stored as an array of indexes instead of a linked list. Assign tags
> > - *    based on objects indexes, so that objects that are next to each other
> > - *    get different tags.
> >   */
> >  static inline u8 assign_tag(struct kmem_cache *cache,
> >                                       const void *object, bool init)
> > @@ -171,17 +167,12 @@ static inline u8 assign_tag(struct kmem_cache *cache,
> >       if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
> >               return init ? KASAN_TAG_KERNEL : kasan_random_tag();
> >
> > -     /* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
> > -#ifdef CONFIG_SLAB
> > -     /* For SLAB assign tags based on the object index in the freelist. */
> > -     return (u8)obj_to_index(cache, virt_to_slab(object), (void *)object);
> > -#else
> >       /*
> > -      * For SLUB assign a random tag during slab creation, otherwise reuse
> > +      * For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU,
> > +      * assign a random tag during slab creation, otherwise reuse
> >        * the already assigned tag.
> >        */
> >       return init ? kasan_random_tag() : get_tag(object);
> > -#endif
> >  }
> >
> >  void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
> > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> > index 8b06bab5c406..eef50233640a 100644
> > --- a/mm/kasan/kasan.h
> > +++ b/mm/kasan/kasan.h
> > @@ -373,8 +373,7 @@ void kasan_set_track(struct kasan_track *track, gfp_t flags);
> >  void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags);
> >  void kasan_save_free_info(struct kmem_cache *cache, void *object);
> >
> > -#if defined(CONFIG_KASAN_GENERIC) && \
> > -     (defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
> > +#ifdef CONFIG_KASAN_GENERIC
> >  bool kasan_quarantine_put(struct kmem_cache *cache, void *object);
> >  void kasan_quarantine_reduce(void);
> >  void kasan_quarantine_remove_cache(struct kmem_cache *cache);
> > diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
> > index ca4529156735..138c57b836f2 100644
> > --- a/mm/kasan/quarantine.c
> > +++ b/mm/kasan/quarantine.c
> > @@ -144,10 +144,6 @@ static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
> >  {
> >       void *object = qlink_to_object(qlink, cache);
> >       struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);
> > -     unsigned long flags;
> > -
> > -     if (IS_ENABLED(CONFIG_SLAB))
> > -             local_irq_save(flags);
> >
> >       /*
> >        * If init_on_free is enabled and KASAN's free metadata is stored in
> > @@ -166,9 +162,6 @@ static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
> >       *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE;
> >
> >       ___cache_free(cache, object, _THIS_IP_);
> > -
> > -     if (IS_ENABLED(CONFIG_SLAB))
> > -             local_irq_restore(flags);
> >  }
> >
> >  static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)
>
> Looks good to me,
> Reviewed-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>

nit: Some KASAN tests depends on SLUB, but as now it's the only allocator
      KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_SLUB); in
      mm/kasan/kasan_test.c can be removed

>
> >
> > --
> > 2.42.1
> >
> >