linux-kernel - [PATCH 4.9 035/109] net/mlx4_en: Fix type mismatch for 32-bit systems

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Date:   Thu,  7 Dec 2017 13:56:19 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Slava Shwartsman <slavash@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 035/109] net/mlx4_en: Fix type mismatch for 32-bit systems

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Slava Shwartsman <slavash@...lanox.com>


[ Upstream commit 61b6034c6cfdcb265bb453505c3d688e7567727a ]

is_power_of_2 expects unsigned long and we pass u64 max_val_cycles,
this will be truncated on 32 bit systems, and the result is not what we
were expecting.
div_u64 expects u32 as a second argument and we pass
max_val_cycles_rounded which is u64 hence it will always be truncated.
Fix was tested on both 64 and 32 bit systems and got same results for
max_val_cycles and max_val_cycles_rounded.

Fixes: 4850cf458157 ("net/mlx4_en: Resolve dividing by zero in 32-bit system")
Signed-off-by: Slava Shwartsman <slavash@...lanox.com>
Signed-off-by: Tariq Toukan <tariqt@...lanox.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/mellanox/mlx4/en_clock.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx4/en_clock.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_clock.c
@@ -251,13 +251,9 @@ static u32 freq_to_shift(u16 freq)
 {
 	u32 freq_khz = freq * 1000;
 	u64 max_val_cycles = freq_khz * 1000 * MLX4_EN_WRAP_AROUND_SEC;
-	u64 tmp_rounded =
-		roundup_pow_of_two(max_val_cycles) > max_val_cycles ?
-		roundup_pow_of_two(max_val_cycles) - 1 : UINT_MAX;
-	u64 max_val_cycles_rounded = is_power_of_2(max_val_cycles + 1) ?
-		max_val_cycles : tmp_rounded;
+	u64 max_val_cycles_rounded = 1ULL << fls64(max_val_cycles - 1);
 	/* calculate max possible multiplier in order to fit in 64bit */
-	u64 max_mul = div_u64(0xffffffffffffffffULL, max_val_cycles_rounded);
+	u64 max_mul = div64_u64(ULLONG_MAX, max_val_cycles_rounded);
 
 	/* This comes from the reverse of clocksource_khz2mult */
 	return ilog2(div_u64(max_mul * freq_khz, 1000000));