Re: [PATCH] mm: workingset: fix NULL ptr dereference

[Johannes Weiner]

On Sun, Apr 08, 2018 at 07:49:25PM -0700, Matthew Wilcox wrote:
> @@ -2714,8 +2714,10 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
>  		stat(s, ALLOC_FASTPATH);
>  	}
>  
> -	if (unlikely(gfpflags & __GFP_ZERO) && object)
> -		memset(object, 0, s->object_size);
> +	if (unlikely(gfpflags & __GFP_ZERO) && object) {
> +		if (!WARN_ON_ONCE(s->ctor))
> +			memset(object, 0, s->object_size);
> +	}
>  
>  	slab_post_alloc_hook(s, gfpflags, 1, &object);

This looks like a useful check to have. But maybe behind DEBUG_VM?