On Sun, Sep 25, 2022 at 02:05:04AM +0800, Andrey Konovalov wrote: > On Wed, Sep 21, 2022 at 2:03 PM Feng Tang <feng.tang@xxxxxxxxx> wrote: > > > > Agree, it's better not touch the internal fields in slub code. > > > > How about the following patch, it merge the 2 functions with one flag > > indicating in meta data or object. (I'm fine with 2 separate functions) > > The overall approach sounds good. See some comments below. > > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > > index b092277bf48d..0ad05a34e708 100644 > > --- a/include/linux/kasan.h > > +++ b/include/linux/kasan.h > > @@ -150,11 +150,12 @@ static __always_inline void kasan_cache_create_kmalloc(struct kmem_cache *cache) > > __kasan_cache_create_kmalloc(cache); > > } > > > > -size_t __kasan_metadata_size(struct kmem_cache *cache); > > -static __always_inline size_t kasan_metadata_size(struct kmem_cache *cache) > > +size_t __kasan_meta_size(struct kmem_cache *cache, bool in_slab_object); > > +static __always_inline size_t kasan_meta_size(struct kmem_cache *cache, > > + bool in_slab_object) > > I would keep the name as kasan_metadata_size as it's more clear to > external users but rename in_slab_object to in_object to make the > declaration shorter. Make sense to me, will do. [...] > > + if (in_slab_object) > > + return (cache->kasan_info.alloc_meta_offset == 0 ? > > + sizeof(struct kasan_alloc_meta) : 0) + > > + (cache->kasan_info.free_meta_offset ? > > + sizeof(struct kasan_free_meta) : 0); > > + else > > + return (cache->kasan_info.alloc_meta_offset == 0 ? > > + sizeof(struct kasan_alloc_meta) : 0) + > > + (cache->kasan_info.free_meta_offset ? > > + sizeof(struct kasan_free_meta) : 0); > > Something weird here: both if and else cases are the same. Yes, will fix it. > The change also needs to be rebased onto [1]. > > Thanks! > > [1] https://lore.kernel.org/linux-mm/c7b316d30d90e5947eb8280f4dc78856a49298cf.1662411799.git.andreyknvl@xxxxxxxxxx/ I noticed this has been merged to -mm tree's 'mm-everything' branch, so following is the patch againt that. Thanks! One thing I'm not very sure is, to check 'in-object' kasan's meta size, I didn't check 'alloc_meta_offset', as from the code reading the alloc_meta is never put inside slab object data area. Thanks, Feng ---8<--- diff --git a/include/linux/kasan.h b/include/linux/kasan.h index d811b3d7d2a1..96c9d56e5510 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -302,7 +302,7 @@ static inline void kasan_unpoison_task_stack(struct task_struct *task) {} #ifdef CONFIG_KASAN_GENERIC -size_t kasan_metadata_size(struct kmem_cache *cache); +size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object); slab_flags_t kasan_never_merge(void); void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, slab_flags_t *flags); @@ -315,7 +315,8 @@ void kasan_record_aux_stack_noalloc(void *ptr); #else /* CONFIG_KASAN_GENERIC */ /* Tag-based KASAN modes do not use per-object metadata. */ -static inline size_t kasan_metadata_size(struct kmem_cache *cache) +static inline size_t kasan_metadata_size(struct kmem_cache *cache, + bool in_object) { return 0; } diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c index d8b5590f9484..5a806f9b9466 100644 --- a/mm/kasan/generic.c +++ b/mm/kasan/generic.c @@ -450,15 +450,22 @@ void kasan_init_object_meta(struct kmem_cache *cache, const void *object) __memset(alloc_meta, 0, sizeof(*alloc_meta)); } -size_t kasan_metadata_size(struct kmem_cache *cache) +size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object) { + struct kasan_cache *info = &cache->kasan_info ; + if (!kasan_requires_meta()) return 0; - return (cache->kasan_info.alloc_meta_offset ? - sizeof(struct kasan_alloc_meta) : 0) + - ((cache->kasan_info.free_meta_offset && - cache->kasan_info.free_meta_offset != KASAN_NO_FREE_META) ? - sizeof(struct kasan_free_meta) : 0); + + if (in_object) + return (info->free_meta_offset ? + 0 : sizeof(struct kasan_free_meta)); + else + return (info->alloc_meta_offset ? + sizeof(struct kasan_alloc_meta) : 0) + + ((info->free_meta_offset && + info->free_meta_offset != KASAN_NO_FREE_META) ? + sizeof(struct kasan_free_meta) : 0); } static void __kasan_record_aux_stack(void *addr, bool can_alloc) diff --git a/mm/slub.c b/mm/slub.c index ce8310e131b3..a75c21a0da8b 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -887,7 +887,7 @@ static void print_trailer(struct kmem_cache *s, struct slab *slab, u8 *p) if (s->flags & SLAB_STORE_USER) off += 2 * sizeof(struct track); - off += kasan_metadata_size(s); + off += kasan_metadata_size(s, false); if (off != size_from_object(s)) /* Beginning of the filler is the free pointer */ @@ -1042,7 +1042,7 @@ static int check_pad_bytes(struct kmem_cache *s, struct slab *slab, u8 *p) /* We also have user information there */ off += 2 * sizeof(struct track); - off += kasan_metadata_size(s); + off += kasan_metadata_size(s, false); if (size_from_object(s) == off) return 1;
