[PATCH net-next] nfp: use struct_size() in kzalloc()

[PATCH net-next] nfp: use struct_size() in kzalloc()

[Gustavo A. R. Silva]

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.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c
index 802c9224bb32..f6f028fa5db9 100644
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c
@@ -269,8 +269,7 @@ __nfp_eth_read_ports(struct nfp_cpp *cpp, struct nfp_nsp *nsp)
 		goto err;
 	}
 
-	table = kzalloc(sizeof(*table) +
-			sizeof(struct nfp_eth_table_port) * cnt, GFP_KERNEL);
+	table = kzalloc(struct_size(table, ports, cnt), GFP_KERNEL);
 	if (!table)
 		goto err;
 
-- 
2.20.1

Re: [PATCH net-next] nfp: use struct_size() in kzalloc()

[Jakub Kicinski]

On Wed, 30 Jan 2019 18:38:59 -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.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>

Re: [PATCH net-next] nfp: use struct_size() in kzalloc()

[Gustavo A. R. Silva]

On 1/30/19 6:52 PM, Jakub Kicinski wrote:
> On Wed, 30 Jan 2019 18:38:59 -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.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> 
> Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> 

Thanks, Jakub.

--
Gustavo

Re: [PATCH net-next] nfp: use struct_size() in kzalloc()

[Joe Perches]

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);

Re: [PATCH net-next] nfp: use struct_size() in kzalloc()

[Gustavo A. R. Silva]

Hi Joe,

On 1/31/19 11:11 AM, Joe Perches wrote:
> 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:
> 

Yep. That's already on my list.

> 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);
> 

I agree.

Thanks
--
Gustavo

Re: [PATCH net-next] nfp: use struct_size() in kzalloc()

[David Miller]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Wed, 30 Jan 2019 18:38:59 -0600

> 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.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Applied.