linux-kernel - [PATCH v2 net] net/mlx4_en: Prevent potential integer overflow calculating Hz

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Message-ID: <aDbFHe19juIJKjsb@stanley.mountain>
Date: Wed, 28 May 2025 11:11:09 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Eugenia Emantayev <eugenia@...lanox.com>
Cc: Tariq Toukan <tariqt@...dia.com>, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Matan Barak <matanb@...lanox.com>, netdev@...r.kernel.org,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH v2 net] net/mlx4_en: Prevent potential integer overflow
 calculating Hz

The "freq" variable is in terms of MHz and "max_val_cycles" is in terms
of Hz.  The fact that "max_val_cycles" is a u64 suggests that support
for high frequency is intended but the "freq_khz * 1000" would overflow
the u32 type if we went above 4GHz.  Use unsigned long long type for the
mutliplication to prevent that.

Fixes: 31c128b66e5b ("net/mlx4_en: Choose time-stamping shift value according to HW frequency")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
v2: Use ULL instead UL.

 drivers/net/ethernet/mellanox/mlx4/en_clock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_clock.c b/drivers/net/ethernet/mellanox/mlx4/en_clock.c
index cd754cd76bde..d73a2044dc26 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_clock.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_clock.c
@@ -249,7 +249,7 @@ static const struct ptp_clock_info mlx4_en_ptp_clock_info = {
 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 max_val_cycles = freq_khz * 1000ULL * MLX4_EN_WRAP_AROUND_SEC;
 	u64 max_val_cycles_rounded = 1ULL << fls64(max_val_cycles - 1);
 	/* calculate max possible multiplier in order to fit in 64bit */
 	u64 max_mul = div64_u64(ULLONG_MAX, max_val_cycles_rounded);
-- 
2.47.2