linux-kernel - Re: [PATCH] IB/srp: Use struct

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Date:   Tue, 08 Jan 2019 12:32:57 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>
Cc:     linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] IB/srp: Use struct_size() in kzalloc()

On Tue, 2019-01-08 at 10:08 -0600, 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 foo {
>     int stuff;
>     void *entry[];
> };
> 
> instance = kzalloc(sizeof(struct foo) + sizeof(void *) * 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, entry, count), GFP_KERNEL);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/infiniband/ulp/srp/ib_srp.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
> index 31d91538bbf4..0f855294ff3f 100644
> --- a/drivers/infiniband/ulp/srp/ib_srp.c
> +++ b/drivers/infiniband/ulp/srp/ib_srp.c
> @@ -443,8 +443,7 @@ static struct srp_fr_pool *srp_create_fr_pool(struct ib_device *device,
>  	if (pool_size <= 0)
>  		goto err;
>  	ret = -ENOMEM;
> -	pool = kzalloc(sizeof(struct srp_fr_pool) +
> -		       pool_size * sizeof(struct srp_fr_desc), GFP_KERNEL);
> +	pool = kzalloc(struct_size(pool, desc, pool_size), GFP_KERNEL);
>  	if (!pool)
>  		goto err;
>  	pool->size = pool_size;

Reviewed-by: Bart Van Assche <bvanassche@....org>