linux-kernel - [PATCH] net: stmmac_tc: use 64-bit arithmetic instead of 32-bit

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Message-ID: <20180702120932.GA13079@embeddedor.com>
Date:   Mon, 2 Jul 2018 07:09:32 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] net: stmmac_tc: use 64-bit arithmetic instead of 32-bit

Add suffix UL to constant 1024 in order to give the compiler complete
information about the proper arithmetic to use. Notice that this
constant is used in a context that expects an expression of type
u64 (64 bits, unsigned) and  following expressions are currently
being evaluated using 32-bit arithmetic:

qopt->idleslope * 1024 * ptr
qopt->hicredit * 1024 * 8
qopt->locredit * 1024 * 8

Addresses-Coverity-ID: 1470246 ("Unintentional integer overflow")
Addresses-Coverity-ID: 1470248 ("Unintentional integer overflow")
Addresses-Coverity-ID: 1470249 ("Unintentional integer overflow")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
index 0b0fca0..8fedc28 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
@@ -321,7 +321,7 @@ static int tc_setup_cbs(struct stmmac_priv *priv,
 	speed_div = (priv->speed == SPEED_100) ? 100000 : 1000000;
 
 	/* Final adjustments for HW */
-	value = qopt->idleslope * 1024 * ptr;
+	value = qopt->idleslope * 1024UL * ptr;
 	do_div(value, speed_div);
 	priv->plat->tx_queues_cfg[queue].idle_slope = value & GENMASK(31, 0);
 
@@ -329,10 +329,10 @@ static int tc_setup_cbs(struct stmmac_priv *priv,
 	do_div(value, speed_div);
 	priv->plat->tx_queues_cfg[queue].send_slope = value & GENMASK(31, 0);
 
-	value = qopt->hicredit * 1024 * 8;
+	value = qopt->hicredit * 1024UL * 8;
 	priv->plat->tx_queues_cfg[queue].high_credit = value & GENMASK(31, 0);
 
-	value = qopt->locredit * 1024 * 8;
+	value = qopt->locredit * 1024UL * 8;
 	priv->plat->tx_queues_cfg[queue].low_credit = value & GENMASK(31, 0);
 
 	ret = stmmac_config_cbs(priv, priv->hw,
-- 
2.7.4