From 6132e89aef51df044246b5aef822144217794ae1 Mon Sep 17 00:00:00 2001 From: Yibo Cai Date: Tue, 4 Aug 2015 14:45:28 +0000 Subject: [PATCH] clk: atlas7: fix integer overflow in dto rate calculation I cannot believe that I spend quite a lot time in finding this bug. It seems a pitfall people tend to fall in. In "int64 = int32 * int32", conversion from 32-bits to 64-bits comes after the multiplication. So this statement may not work as expected. Signed-off-by: Yibo Cai Signed-off-by: Barry Song Signed-off-by: Stephen Boyd --- drivers/clk/sirf/clk-atlas7.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/clk/sirf/clk-atlas7.c b/drivers/clk/sirf/clk-atlas7.c index 07b970ff50f1..ed77fd51692c 100644 --- a/drivers/clk/sirf/clk-atlas7.c +++ b/drivers/clk/sirf/clk-atlas7.c @@ -519,7 +519,7 @@ static unsigned long dto_clk_recalc_rate(struct clk_hw *hw, static long dto_clk_round_rate(struct clk_hw *hw, unsigned long rate, unsigned long *parent_rate) { - u64 dividend = rate * (1 << 29); + u64 dividend = (u64)rate * (1 << 29); do_div(dividend, *parent_rate); dividend *= *parent_rate; @@ -531,7 +531,7 @@ static long dto_clk_round_rate(struct clk_hw *hw, unsigned long rate, static int dto_clk_set_rate(struct clk_hw *hw, unsigned long rate, unsigned long parent_rate) { - u64 dividend = rate * (1 << 29); + u64 dividend = (u64)rate * (1 << 29); struct clk_dto *clk = to_dtoclk(hw); do_div(dividend, parent_rate); -- 2.20.1