linux-kernel - Re: [PATCH] libnvdimm, region: Use struct

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Date:   Wed, 28 Aug 2019 13:30:24 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Keith Busch <keith.busch@...el.com>,
        Ira Weiny <ira.weiny@...el.com>
Cc:     linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] libnvdimm, region: Use struct_size() in kzalloc()

Hi all,

Friendly ping:

Who can take this, please?

Thanks
--
Gustavo

On 6/10/19 4:06 PM, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
> 
> struct nd_region {
> 	...
>         struct nd_mapping mapping[0];
> };
> 
> instance = kzalloc(sizeof(struct nd_region) + sizeof(struct nd_mapping) *
>                           count, GFP_KERNEL);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> instance = kzalloc(struct_size(instance, mapping, count), GFP_KERNEL);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/nvdimm/region_devs.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index b4ef7d9ff22e..88becc87e234 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -1027,10 +1027,9 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
>  		}
>  		region_buf = ndbr;
>  	} else {
> -		nd_region = kzalloc(sizeof(struct nd_region)
> -				+ sizeof(struct nd_mapping)
> -				* ndr_desc->num_mappings,
> -				GFP_KERNEL);
> +		nd_region = kzalloc(struct_size(nd_region, mapping,
> +						ndr_desc->num_mappings),
> +				    GFP_KERNEL);
>  		region_buf = nd_region;
>  	}
>  
>