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

[Vlastimil Babka]

On 12/5/23 05:48, Hyeonggon Yoo wrote:
> 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>

Thanks!

> 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

Hmm I see, but will rather also leave it for later cleanup at this point,
thanks!

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