linux-kernel - [PATCH] iwlwifi: d3: use struct

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Message-ID: <20180824011540.GA25716@embeddedor.com>
Date:   Thu, 23 Aug 2018 20:15:40 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Johannes Berg <johannes.berg@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Intel Linux Wireless <linuxwifi@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] iwlwifi: d3: 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 issue was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/net/wireless/intel/iwlwifi/mvm/d3.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/d3.c b/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
index 79bdae9..6960318 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
@@ -1769,8 +1769,7 @@ static void iwl_mvm_query_netdetect_reasons(struct iwl_mvm *mvm,
 		n_matches = 0;
 	}
 
-	net_detect = kzalloc(sizeof(*net_detect) +
-			     (n_matches * sizeof(net_detect->matches[0])),
+	net_detect = kzalloc(struct_size(net_detect, matches, n_matches),
 			     GFP_KERNEL);
 	if (!net_detect || !n_matches)
 		goto out_report_nd;
@@ -1785,8 +1784,7 @@ static void iwl_mvm_query_netdetect_reasons(struct iwl_mvm *mvm,
 		for (j = 0; j < SCAN_OFFLOAD_MATCHING_CHANNELS_LEN; j++)
 			n_channels += hweight8(fw_match->matching_channels[j]);
 
-		match = kzalloc(sizeof(*match) +
-				(n_channels * sizeof(*match->channels)),
+		match = kzalloc(struct_size(match, channels, n_channels),
 				GFP_KERNEL);
 		if (!match)
 			goto out_report_nd;
-- 
2.7.4