netdev - re: [PATCH] cfg80211: read wmm rules from regulatory database

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Message-ID: <9ff30f03-07f1-0abd-8c57-2601af546de0@canonical.com>
Date:   Tue, 31 Jul 2018 12:27:54 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Haim Dreyfuss <haim.dreyfuss@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Johannes Berg <johannes@...solutions.net>,
        netdev@...r.kernel.org,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: re: [PATCH] cfg80211: read wmm rules from regulatory database

Hi Haim,

I think there may be an issue with the commit:

>From 230ebaa189af44d50dccb4a1846e39ca594e347b Mon Sep 17 00:00:00 2001
From: Haim Dreyfuss <haim.dreyfuss@...el.com>
Date: Wed, 28 Mar 2018 13:24:09 +0300
Subject: [PATCH] cfg80211: read wmm rules from regulatory database

specifically in function: reg_copy_regd()

+       for (i = 0; i < src_regd->n_reg_rules; i++) {
                memcpy(&regd->reg_rules[i], &src_regd->reg_rules[i],
                       sizeof(struct ieee80211_reg_rule));
+               if (!src_regd->reg_rules[i].wmm_rule)
+                       continue;

+               regd->reg_rules[i].wmm_rule = d_wmm +
+                       (src_regd->reg_rules[i].wmm_rule - s_wmm) /
+                       sizeof(struct ieee80211_wmm_rule);
+       }

The pointer arithmetic (src_regd->reg_rules[i].wmm_rule - s_wmm) is
performed in terms of the size of struct ieee80211_wmm_rule and not in
bytes and I believe that the division by sizeof(struct
ieee80211_wmm_rule) is not required.

This issue was detected by static analysis with Coverity Scan,
CID#1467451 ("Extra sizeof expression"), 'suspicious_division'

I'm not 100% sure that is this a false positive or not, but I think it
looks incorrect to me.

Colin