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

[PATCH] iwlwifi: nvm-parse: 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;
    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@embeddedor.com>
---
 .../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

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

[Luciano Coelho]

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 <gustavo@embeddedor.com>
> ---

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

--
Cheers,
Luca.