netdev - [PATCH] net: phy: mdio-bcm-unimac: Cast denominator to unsigned long to avoid overflow

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Date: Thu, 7 Mar 2024 16:19:47 +0300
From: Daniil Dulov <d.dulov@...ddin.ru>
To: Doug Berger <opendmb@...il.com>
CC: Daniil Dulov <d.dulov@...ddin.ru>, Florian Fainelli
	<florian.fainelli@...adcom.com>, Broadcom internal kernel review list
	<bcm-kernel-feedback-list@...adcom.com>, Andrew Lunn <andrew@...n.ch>, Heiner
 Kallweit <hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<lvc-project@...uxtesting.org>
Subject: [PATCH] net: phy: mdio-bcm-unimac: Cast denominator to unsigned long to avoid overflow

The expression priv->clk_freq * 2 can lead to overflow that will cause
a division by zero. So, let's cast it to unsigned long to avoid it.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: b78ac6ecd1b6 ("net: phy: mdio-bcm-unimac: Allow configuring MDIO clock divider")
Signed-off-by: Daniil Dulov <d.dulov@...ddin.ru>
---
 drivers/net/mdio/mdio-bcm-unimac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/mdio/mdio-bcm-unimac.c b/drivers/net/mdio/mdio-bcm-unimac.c
index 68f8ee0ec8ba..055102e6bb6d 100644
--- a/drivers/net/mdio/mdio-bcm-unimac.c
+++ b/drivers/net/mdio/mdio-bcm-unimac.c
@@ -192,7 +192,7 @@ static void unimac_mdio_clk_set(struct unimac_mdio_priv *priv)
 	else
 		rate = clk_get_rate(priv->clk);
 
-	div = (rate / (2 * priv->clk_freq)) - 1;
+	div = (rate / (2 * (unsigned long)priv->clk_freq)) - 1;
 	if (div & ~MDIO_CLK_DIV_MASK) {
 		pr_warn("Incorrect MDIO clock frequency, ignoring\n");
 		return;
-- 
2.25.1