netdev - [PATCH] mac80211: fix potential overflow when multiplying to u32 integers

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Date:   Fri,  5 Feb 2021 17:53:52 +0000
From:   Colin King <colin.king@...onical.com>
To:     Johannes Berg <johannes@...solutions.net>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "John W . Linville" <linville@...driver.com>,
        Luis Carlos Cobo <luisca@...ybit.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mac80211: fix potential overflow when multiplying to u32 integers

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

The multiplication of the u32 variables tx_time and estimated_retx is
performed using a 32 bit multiplication and the result is stored in
a u64 result. This has a potential u32 overflow issue, so avoid this
by casting tx_time to a u64 to force a 64 bit multiply.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: 050ac52cbe1f ("mac80211: code for on-demand Hybrid Wireless Mesh Protocol")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 net/mac80211/mesh_hwmp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 313eee12410e..3db514c4c63a 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -356,7 +356,7 @@ u32 airtime_link_metric_get(struct ieee80211_local *local,
 	 */
 	tx_time = (device_constant + 10 * test_frame_len / rate);
 	estimated_retx = ((1 << (2 * ARITH_SHIFT)) / (s_unit - err));
-	result = (tx_time * estimated_retx) >> (2 * ARITH_SHIFT);
+	result = ((u64)tx_time * estimated_retx) >> (2 * ARITH_SHIFT);
 	return (u32)result;
 }
 
-- 
2.29.2