Subject: Re: [PATCH net] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 8 Feb 2018 17:44:48 +0200

On Wed, Feb 07, 2018 at 04:08:25PM +0800, Jason Wang wrote:
> To avoid slab to warn about exceeded size, fail early if queue
> occupies more than KMALLOC_MAX_SIZE.
> 
> Reported-by: [email-masked]
> Signed-off-by: Jason Wang <[email-masked]>
> ---
>  include/linux/ptr_ring.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> index 1883d61..4b862da 100644
> --- a/include/linux/ptr_ring.h
> +++ b/include/linux/ptr_ring.h
> @@ -466,6 +466,8 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
>  
>  static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
>  {
> +	if (size > KMALLOC_MAX_SIZE)
> +		return NULL;
>  	return kcalloc(size, sizeof(void *), gfp);
>  }

I guess this approach does begin to make more sense
at least as a temporary stop-gap.

But does this actually prevent the crash in all cases?

size is in void* entry units, KMALLOC_MAX_SIZE is in bytes.

> -- 
> 2.7.4