On Mon, 2020-05-18 at 12:18 +0200, Dmitry Vyukov wrote: > On Mon, May 18, 2020 at 8:27 AM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > > > Move free track from slub alloc meta-data to slub free meta-data in > > order to make struct kasan_free_meta size is 16 bytes. It is a good > > size because it is the minimal redzone size and a good number of > > alignment. > > > > For free track in generic KASAN, we do the modification in struct > > kasan_alloc_meta and kasan_free_meta: > > - remove free track from kasan_alloc_meta. > > - add free track into kasan_free_meta. > > > > [1]https://bugzilla.kernel.org/show_bug.cgi?id=198437 > > > > Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> > > Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> > > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > Cc: Alexander Potapenko <glider@xxxxxxxxxx> > > --- > > mm/kasan/common.c | 33 ++++++++++----------------------- > > mm/kasan/generic.c | 18 ++++++++++++++++++ > > mm/kasan/kasan.h | 7 +++++++ > > mm/kasan/report.c | 20 -------------------- > > mm/kasan/tags.c | 37 +++++++++++++++++++++++++++++++++++++ > > 5 files changed, 72 insertions(+), 43 deletions(-) > > > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > > index 8bc618289bb1..6500bc2bb70c 100644 > > --- a/mm/kasan/common.c > > +++ b/mm/kasan/common.c > > @@ -51,7 +51,7 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags) > > return stack_depot_save(entries, nr_entries, flags); > > } > > > > -static inline void set_track(struct kasan_track *track, gfp_t flags) > > +void kasan_set_track(struct kasan_track *track, gfp_t flags) > > { > > track->pid = current->pid; > > track->stack = kasan_save_stack(flags); > > @@ -249,9 +249,7 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, > > *size += sizeof(struct kasan_alloc_meta); > > > > /* Add free meta. */ > > - if (IS_ENABLED(CONFIG_KASAN_GENERIC) && > > - (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor || > > - cache->object_size < sizeof(struct kasan_free_meta))) { > > + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) { > > Why do we need to increase object size unconditionally? > We only store info in free track when the object is free, so I would > assume we still can generally overlap free track and the object > itself. We store free track at the same time we use the quarantine > link, and the quarantine link was overlapped with the object just > fine. > With this change we indeed increase object size, which we do not want > in general. > If it doesn't add free meta, but we always store free track into the object, Is it safe? > > > cache->kasan_info.free_meta_offset = *size; > > *size += sizeof(struct kasan_free_meta); > > } > > @@ -299,24 +297,6 @@ struct kasan_free_meta *get_free_info(struct kmem_cache *cache, > > return (void *)object + cache->kasan_info.free_meta_offset; > > } > > > > - > > -static void kasan_set_free_info(struct kmem_cache *cache, > > - void *object, u8 tag) > > -{ > > - struct kasan_alloc_meta *alloc_meta; > > - u8 idx = 0; > > - > > - alloc_meta = get_alloc_info(cache, object); > > - > > -#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY > > - idx = alloc_meta->free_track_idx; > > - alloc_meta->free_pointer_tag[idx] = tag; > > - alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS; > > -#endif > > - > > - set_track(&alloc_meta->free_track[idx], GFP_NOWAIT); > > -} > > - > > void kasan_poison_slab(struct page *page) > > { > > unsigned long i; > > @@ -396,6 +376,13 @@ void * __must_check kasan_init_slab_obj(struct kmem_cache *cache, > > alloc_info = get_alloc_info(cache, object); > > __memset(alloc_info, 0, sizeof(*alloc_info)); > > > > + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) { > > + struct kasan_free_meta *free_info; > > + > > + free_info = get_free_info(cache, object); > > + __memset(free_info, 0, sizeof(*free_info)); > > If we overlap free track with object, this will not be needed as well, right? > Should we not consider those objects which have adding free meta? If they exist, then we should init their meta data when object re-allocate. struct kasan_free_meta { struct qlist_node quarantine_link; struct kasan_track free_track; }; > > + } > > + > > if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) > > object = set_tag(object, > > assign_tag(cache, object, true, false)); > > @@ -492,7 +479,7 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object, > > KASAN_KMALLOC_REDZONE); > > > > if (cache->flags & SLAB_KASAN) > > - set_track(&get_alloc_info(cache, object)->alloc_track, flags); > > + kasan_set_track(&get_alloc_info(cache, object)->alloc_track, flags); > > > > return set_tag(object, tag); > > } > > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > > index 78d8e0a75a8a..988bc095b738 100644 > > --- a/mm/kasan/generic.c > > +++ b/mm/kasan/generic.c > > @@ -345,3 +345,21 @@ void kasan_record_aux_stack(void *addr) > > alloc_info->rcu_stack[1] = alloc_info->rcu_stack[0]; > > alloc_info->rcu_stack[0] = kasan_save_stack(GFP_NOWAIT); > > } > > + > > +void kasan_set_free_info(struct kmem_cache *cache, > > + void *object, u8 tag) > > +{ > > + struct kasan_free_meta *free_meta; > > + > > + free_meta = get_free_info(cache, object); > > + kasan_set_track(&free_meta->free_track, GFP_NOWAIT); > > +} > > + > > +struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, > > + void *object, u8 tag) > > +{ > > + struct kasan_free_meta *free_meta; > > + > > + free_meta = get_free_info(cache, object); > > + return &free_meta->free_track; > > +} > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > > index 870c5dd07756..87ee3626b8b0 100644 > > --- a/mm/kasan/kasan.h > > +++ b/mm/kasan/kasan.h > > @@ -127,6 +127,9 @@ struct kasan_free_meta { > > * Otherwise it might be used for the allocator freelist. > > */ > > struct qlist_node quarantine_link; > > +#ifdef CONFIG_KASAN_GENERIC > > + struct kasan_track free_track; > > +#endif > > }; > > > > struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache, > > @@ -168,6 +171,10 @@ void kasan_report_invalid_free(void *object, unsigned long ip); > > struct page *kasan_addr_to_page(const void *addr); > > > > depot_stack_handle_t kasan_save_stack(gfp_t flags); > > +void kasan_set_track(struct kasan_track *track, gfp_t flags); > > +void kasan_set_free_info(struct kmem_cache *cache, void *object, u8 tag); > > +struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, > > + void *object, u8 tag); > > > > #if defined(CONFIG_KASAN_GENERIC) && \ > > (defined(CONFIG_SLAB) || defined(CONFIG_SLUB)) > > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > > index 5ee66cf7e27c..7e9f9f6d5e85 100644 > > --- a/mm/kasan/report.c > > +++ b/mm/kasan/report.c > > @@ -159,26 +159,6 @@ static void describe_object_addr(struct kmem_cache *cache, void *object, > > (void *)(object_addr + cache->object_size)); > > } > > > > -static struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, > > - void *object, u8 tag) > > -{ > > - struct kasan_alloc_meta *alloc_meta; > > - int i = 0; > > - > > - alloc_meta = get_alloc_info(cache, object); > > - > > -#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY > > - for (i = 0; i < KASAN_NR_FREE_STACKS; i++) { > > - if (alloc_meta->free_pointer_tag[i] == tag) > > - break; > > - } > > - if (i == KASAN_NR_FREE_STACKS) > > - i = alloc_meta->free_track_idx; > > -#endif > > - > > - return &alloc_meta->free_track[i]; > > -} > > - > > #ifdef CONFIG_KASAN_GENERIC > > static void print_stack(depot_stack_handle_t stack) > > { > > diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c > > index 25b7734e7013..201dee5d6ae0 100644 > > --- a/mm/kasan/tags.c > > +++ b/mm/kasan/tags.c > > @@ -162,3 +162,40 @@ void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size) > > kasan_poison_shadow((void *)addr, size, tag); > > } > > EXPORT_SYMBOL(__hwasan_tag_memory); > > + > > +void kasan_set_free_info(struct kmem_cache *cache, > > + void *object, u8 tag) > > +{ > > + struct kasan_alloc_meta *alloc_meta; > > + u8 idx = 0; > > + > > + alloc_meta = get_alloc_info(cache, object); > > + > > +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY > > + idx = alloc_meta->free_track_idx; > > + alloc_meta->free_pointer_tag[idx] = tag; > > + alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS; > > +#endif > > + > > + kasan_set_track(&alloc_meta->free_track[idx], GFP_NOWAIT); > > +} > > + > > +struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, > > + void *object, u8 tag) > > +{ > > + struct kasan_alloc_meta *alloc_meta; > > + int i = 0; > > + > > + alloc_meta = get_alloc_info(cache, object); > > + > > +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY > > + for (i = 0; i < KASAN_NR_FREE_STACKS; i++) { > > + if (alloc_meta->free_pointer_tag[i] == tag) > > + break; > > + } > > + if (i == KASAN_NR_FREE_STACKS) > > + i = alloc_meta->free_track_idx; > > +#endif > > + > > + return &alloc_meta->free_track[i]; > > +} > > -- > > 2.18.0
