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

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

[Dan Carpenter]

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@linaro.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

Re: [PATCH v2 net] net/mlx4_en: Prevent potential integer overflow calculating Hz

[Simon Horman]

On Wed, May 28, 2025 at 11:11:09AM +0300, Dan Carpenter wrote:
> 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@linaro.org>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH v2 net] net/mlx4_en: Prevent potential integer overflow calculating Hz

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Wed, 28 May 2025 11:11:09 +0300 you wrote:
> 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@linaro.org>
> 
> [...]

Here is the summary with links:
  - [v2,net] net/mlx4_en: Prevent potential integer overflow calculating Hz
    https://git.kernel.org/netdev/net/c/54d34165b4f7

You are awesome, thank you!
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