linux-kernel - [PATCH][next] clk: imx: pll14xx: Fix potential integer overflow on multiplication

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Message-Id: <20241007084840.1167527-1-colin.i.king@gmail.com>
Date: Mon,  7 Oct 2024 09:48:40 +0100
From: Colin Ian King <colin.i.king@...il.com>
To: Abel Vesa <abelvesa@...nel.org>,
	Peng Fan <peng.fan@....com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	linux-clk@...r.kernel.org,
	imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org
Cc: kernel-janitors@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH][next] clk: imx: pll14xx: Fix potential integer overflow on multiplication

The calculation of fout is using int multiplication and assigning
the result to a u64, this can potentially overflow if the int variable
mdiv is too large. Fix this by making the 65536 a u64 value to ensure a
u64 multiplication is being performed to avoid the overflow.

Fixes: 53990cf9d5b4 ("clk: imx: pll14xx: consolidate rate calculation")
Signed-off-by: Colin Ian King <colin.i.king@...il.com>
---
 drivers/clk/imx/clk-pll14xx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index d63564dbb12c..2afe361fc711 100644
--- a/drivers/clk/imx/clk-pll14xx.c
+++ b/drivers/clk/imx/clk-pll14xx.c
@@ -107,7 +107,7 @@ static long pll14xx_calc_rate(struct clk_pll14xx *pll, int mdiv, int pdiv,
 	u64 fout = prate;
 
 	/* fout = (m * 65536 + k) * Fin / (p * 65536) / (1 << sdiv) */
-	fout *= (mdiv * 65536 + kdiv);
+	fout *= (mdiv * 65536ULL + kdiv);
 	pdiv *= 65536;
 
 	do_div(fout, pdiv << sdiv);
-- 
2.46.2