linux-kernel - Re: [PATCH net-next] nfp: use struct

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Date:   Thu, 31 Jan 2019 09:11:12 -0800
From:   Joe Perches <joe@...ches.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     oss-drivers@...ronome.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] nfp: use struct_size() in kzalloc()

On Wed, 2019-01-30 at 18:38 -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;
>     struct boo entry[];
> };
> 
> instance = kzalloc(sizeof(struct foo) + count * sizeof(struct boo), 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.

Might be useful to augment the script to include cases
where the computed size is saved to a temporary and
that temporary is used ala:

https://patchwork.kernel.org/patch/10782453/

On Sat, 2019-01-26 at 20:42 +0800, YueHaibing wrote:
> Use kmemdup rather than duplicating its implementation
[]
> diff --git a/drivers/net/wireless/intel/iwlwifi/iwl-nvm-parse.c b/drivers/net/wireless/intel/iwlwifi/iwl-nvm-parse.c
[]
> @@ -1196,13 +1196,9 @@ iwl_parse_nvm_mcc_info(struct device *dev, const struct iwl_cfg *cfg,
>  	regd_to_copy = sizeof(struct ieee80211_regdomain) +
>  		valid_rules * sizeof(struct ieee80211_reg_rule);
> -	copy_rd = kzalloc(regd_to_copy, GFP_KERNEL);
> -	if (!copy_rd) {
> +	copy_rd = kmemdup(regd, regd_to_copy, GFP_KERNEL);

This should probably be

	copy_rd = kmemdup(regd, struct_size(regd, reg_rules, valid_rules),
			  GFP_KERNEL);