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Tue, 02 Feb 2021 08:06:28 -0800 (PST) Date: Tue, 2 Feb 2021 17:06:21 +0100 From: Marco Elver To: Andrey Konovalov Cc: Catalin Marinas , Vincenzo Frascino , Dmitry Vyukov , Alexander Potapenko , Andrew Morton , Will Deacon , Andrey Ryabinin , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 01/12] kasan, mm: don't save alloc stacks twice Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.0.2 (2020-11-20) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Feb 01, 2021 at 08:43PM +0100, Andrey Konovalov wrote: > Currently KASAN saves allocation stacks in both kasan_slab_alloc() and > kasan_kmalloc() annotations. This patch changes KASAN to save allocation > stacks for slab objects from kmalloc caches in kasan_kmalloc() only, > and stacks for other slab objects in kasan_slab_alloc() only. > > This change requires ____kasan_kmalloc() knowing whether the object > belongs to a kmalloc cache. This is implemented by adding a flag field > to the kasan_info structure. That flag is only set for kmalloc caches > via a new kasan_cache_create_kmalloc() annotation. > > Signed-off-by: Andrey Konovalov Reviewed-by: Marco Elver > --- > include/linux/kasan.h | 9 +++++++++ > mm/kasan/common.c | 18 ++++++++++++++---- > mm/slab_common.c | 1 + > 3 files changed, 24 insertions(+), 4 deletions(-) > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > index 6d8f3227c264..2d5de4092185 100644 > --- a/include/linux/kasan.h > +++ b/include/linux/kasan.h > @@ -83,6 +83,7 @@ static inline void kasan_disable_current(void) {} > struct kasan_cache { > int alloc_meta_offset; > int free_meta_offset; > + bool is_kmalloc; > }; > > #ifdef CONFIG_KASAN_HW_TAGS > @@ -143,6 +144,13 @@ static __always_inline void kasan_cache_create(struct kmem_cache *cache, > __kasan_cache_create(cache, size, flags); > } > > +void __kasan_cache_create_kmalloc(struct kmem_cache *cache); > +static __always_inline void kasan_cache_create_kmalloc(struct kmem_cache *cache) > +{ > + if (kasan_enabled()) > + __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) > { > @@ -278,6 +286,7 @@ static inline void kasan_free_pages(struct page *page, unsigned int order) {} > static inline void kasan_cache_create(struct kmem_cache *cache, > unsigned int *size, > slab_flags_t *flags) {} > +static inline void kasan_cache_create_kmalloc(struct kmem_cache *cache) {} > static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; } > static inline void kasan_poison_slab(struct page *page) {} > static inline void kasan_unpoison_object_data(struct kmem_cache *cache, > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index fe852f3cfa42..374049564ea3 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -210,6 +210,11 @@ void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size, > *size = optimal_size; > } > > +void __kasan_cache_create_kmalloc(struct kmem_cache *cache) > +{ > + cache->kasan_info.is_kmalloc = true; > +} > + > size_t __kasan_metadata_size(struct kmem_cache *cache) > { > if (!kasan_stack_collection_enabled()) > @@ -394,17 +399,22 @@ void __kasan_slab_free_mempool(void *ptr, unsigned long ip) > } > } > > -static void set_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags) > +static void set_alloc_info(struct kmem_cache *cache, void *object, > + gfp_t flags, bool kmalloc) > { > struct kasan_alloc_meta *alloc_meta; > > + /* Don't save alloc info for kmalloc caches in kasan_slab_alloc(). */ > + if (cache->kasan_info.is_kmalloc && !kmalloc) > + return; > + > alloc_meta = kasan_get_alloc_meta(cache, object); > if (alloc_meta) > kasan_set_track(&alloc_meta->alloc_track, flags); > } > > static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object, > - size_t size, gfp_t flags, bool keep_tag) > + size_t size, gfp_t flags, bool kmalloc) > { > unsigned long redzone_start; > unsigned long redzone_end; > @@ -423,7 +433,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object, > KASAN_GRANULE_SIZE); > redzone_end = round_up((unsigned long)object + cache->object_size, > KASAN_GRANULE_SIZE); > - tag = assign_tag(cache, object, false, keep_tag); > + tag = assign_tag(cache, object, false, kmalloc); > > /* Tag is ignored in set_tag without CONFIG_KASAN_SW/HW_TAGS */ > kasan_unpoison(set_tag(object, tag), size); > @@ -431,7 +441,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object, > KASAN_KMALLOC_REDZONE); > > if (kasan_stack_collection_enabled()) > - set_alloc_info(cache, (void *)object, flags); > + set_alloc_info(cache, (void *)object, flags, kmalloc); It doesn't bother me too much, but: 'bool kmalloc' shadows function 'kmalloc' so this is technically fine, but using 'kmalloc' as the variable name here might be confusing and there is a small chance it might cause problems in a future refactor. > return set_tag(object, tag); > } > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 9aa3d2fe4c55..39d1a8ff9bb8 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -647,6 +647,7 @@ struct kmem_cache *__init create_kmalloc_cache(const char *name, > panic("Out of memory when creating slab %s\n", name); > > create_boot_cache(s, name, size, flags, useroffset, usersize); > + kasan_cache_create_kmalloc(s); > list_add(&s->list, &slab_caches); > s->refcount = 1; > return s; > -- > 2.30.0.365.g02bc693789-goog >