linux-kernel - [PATCH] mac80211: ethtool: avoid 32 bit multiplication overflow

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Message-Id: <20180508125732.5153-1-colin.king@canonical.com>
Date:   Tue,  8 May 2018 13:57:32 +0100
From:   Colin King <colin.king@...onical.com>
To:     Johannes Berg <johannes@...solutions.net>,
        "David S . Miller" <davem@...emloft.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mac80211: ethtool: avoid 32 bit multiplication overflow

From: Colin Ian King <colin.king@...onical.com>

The multiplication of 100000 * cfg80211_calculate_bitrate() is a 32 bit
operation and can overflow if cfg80211_calculate_bitrate is greater
than 42949. Although I don't believe this is occurring at present, it
would be safer to avoid the potential overflow by making the constant
100000 an ULL to ensure a 64 multiplication occurs.

Detected by CoverityScan, CID#1468643 ("Unintentional integer overflow")

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 net/mac80211/ethtool.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/ethtool.c b/net/mac80211/ethtool.c
index 08408520c3f8..2ba5686cbcab 100644
--- a/net/mac80211/ethtool.c
+++ b/net/mac80211/ethtool.c
@@ -117,11 +117,11 @@ static void ieee80211_get_stats(struct net_device *dev,
 
 
 		if (sinfo.filled & BIT(NL80211_STA_INFO_TX_BITRATE))
-			data[i] = 100000 *
+			data[i] = 100000ULL *
 				cfg80211_calculate_bitrate(&sinfo.txrate);
 		i++;
 		if (sinfo.filled & BIT(NL80211_STA_INFO_RX_BITRATE))
-			data[i] = 100000 *
+			data[i] = 100000ULL *
 				cfg80211_calculate_bitrate(&sinfo.rxrate);
 		i++;
 
-- 
2.17.0