2019-01-31 00:40:49

by Gustavo A. R. Silva

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

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 <[email protected]>
---
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



2019-01-31 00:54:42

by Jakub Kicinski

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

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 <[email protected]>

Acked-by: Jakub Kicinski <[email protected]>

2019-01-31 00:58:50

by Gustavo A. R. Silva

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



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 <[email protected]>
>
> Acked-by: Jakub Kicinski <[email protected]>
>

Thanks, Jakub.

--
Gustavo

2019-01-31 17:39:17

by Joe Perches

[permalink] [raw]
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);




2019-01-31 17:39:37

by Gustavo A. R. Silva

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

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

2019-02-01 23:23:27

by David Miller

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

From: "Gustavo A. R. Silva" <[email protected]>
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 <[email protected]>

Applied.