2019-01-08 18:19:15

by Gustavo A. R. Silva

Subject: [PATCH] iwlwifi: nvm-parse: 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;
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 <[email protected]>
---
.../net/wireless/intel/iwlwifi/iwl-nvm-parse.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/iwl-nvm-parse.c b/drivers/net/wireless/intel/iwlwifi/iwl-nvm-parse.c
index d9afedc3d1d9..8c720b42dc36 100644
--- a/drivers/net/wireless/intel/iwlwifi/iwl-nvm-parse.c
+++ b/drivers/net/wireless/intel/iwlwifi/iwl-nvm-parse.c
@@ -947,15 +947,13 @@ iwl_parse_nvm_data(struct iwl_trans *trans, const struct iwl_cfg *cfg,
const __le16 *ch_section;

if (cfg->nvm_type != IWL_NVM_EXT)
- data = kzalloc(sizeof(*data) +
- sizeof(struct ieee80211_channel) *
- IWL_NVM_NUM_CHANNELS,
- GFP_KERNEL);
+ data = kzalloc(struct_size(data, channels,
+ IWL_NVM_NUM_CHANNELS),
+ GFP_KERNEL);
else
- data = kzalloc(sizeof(*data) +
- sizeof(struct ieee80211_channel) *
- IWL_NVM_NUM_CHANNELS_EXT,
- GFP_KERNEL);
+ data = kzalloc(struct_size(data, channels,
+ IWL_NVM_NUM_CHANNELS_EXT),
+ GFP_KERNEL);
if (!data)
return NULL;

@@ -1444,9 +1442,7 @@ struct iwl_nvm_data *iwl_get_nvm(struct iwl_trans *trans,
if (empty_otp)
IWL_INFO(trans, "OTP is empty\n");

- nvm = kzalloc(sizeof(*nvm) +
- sizeof(struct ieee80211_channel) * IWL_NUM_CHANNELS,
- GFP_KERNEL);
+ nvm = kzalloc(struct_size(nvm, channels, IWL_NUM_CHANNELS), GFP_KERNEL);
if (!nvm) {
ret = -ENOMEM;
goto out;
--
2.20.1

2019-01-22 10:57:08

by Luciano Coelho

Subject: Re: [PATCH] iwlwifi: nvm-parse: use struct_size() in kzalloc()

On Tue, 2019-01-08 at 11:55 -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 <[email protected]>
> ---

Thanks! I applied this to our internal tree and it will reach the
mainline following our normal upstreaming process.

--
Cheers,
Luca.