Re: [PATCH 2/5] kasan, kmemleak: pass tagged pointers to kmemleak

[Vincenzo Frascino <vincenzo.frascino@arm.com>]

On 11/02/2019 21:59, Andrey Konovalov wrote:
> Right now we call kmemleak hooks before assigning tags to pointers in
> KASAN hooks. As a result, when an objects gets allocated, kmemleak sees
> a differently tagged pointer, compared to the one it sees when the object
> gets freed. Fix it by calling KASAN hooks before kmemleak's ones.
>

Nit: Could you please add comments to the the code? It should prevent that the
code gets refactored in future, reintroducing the same issue.

> Reported-by: Qian Cai <cai@lca.pw>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
>  mm/slab.h        | 6 ++----
>  mm/slab_common.c | 2 +-
>  mm/slub.c        | 3 ++-
>  3 files changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/slab.h b/mm/slab.h
> index 4190c24ef0e9..638ea1b25d39 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -437,11 +437,9 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
>  
>  	flags &= gfp_allowed_mask;
>  	for (i = 0; i < size; i++) {
> -		void *object = p[i];
> -
> -		kmemleak_alloc_recursive(object, s->object_size, 1,
> +		p[i] = kasan_slab_alloc(s, p[i], flags);
> +		kmemleak_alloc_recursive(p[i], s->object_size, 1,
>  					 s->flags, flags);
> -		p[i] = kasan_slab_alloc(s, object, flags);
>  	}
>  
>  	if (memcg_kmem_enabled())
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 81732d05e74a..fe524c8d0246 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1228,8 +1228,8 @@ void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
>  	flags |= __GFP_COMP;
>  	page = alloc_pages(flags, order);
>  	ret = page ? page_address(page) : NULL;
> -	kmemleak_alloc(ret, size, 1, flags);
>  	ret = kasan_kmalloc_large(ret, size, flags);
> +	kmemleak_alloc(ret, size, 1, flags);
>  	return ret;
>  }
>  EXPORT_SYMBOL(kmalloc_order);
> diff --git a/mm/slub.c b/mm/slub.c
> index 1e3d0ec4e200..4a3d7686902f 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1374,8 +1374,9 @@ static inline void dec_slabs_node(struct kmem_cache *s, int node,
>   */
>  static inline void *kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
>  {
> +	ptr = kasan_kmalloc_large(ptr, size, flags);
>  	kmemleak_alloc(ptr, size, 1, flags);
> -	return kasan_kmalloc_large(ptr, size, flags);
> +	return ptr;
>  }
>  
>  static __always_inline void kfree_hook(void *x)
> 

-- 
Regards,
Vincenzo