2021-09-04 15:28:44

by Len Baker

Subject: [PATCH] cpufreq: powernow: Prefer kcalloc over open coded arithmetic

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the purpose specific kcalloc() function instead of the argument
size * count in the kzalloc() function.

[1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <[email protected]>
---
drivers/cpufreq/powernow-k7.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/powernow-k7.c b/drivers/cpufreq/powernow-k7.c
index 5d515fc34836..a9d2c7bae235 100644
--- a/drivers/cpufreq/powernow-k7.c
+++ b/drivers/cpufreq/powernow-k7.c
@@ -174,8 +174,8 @@ static int get_ranges(unsigned char *pst)
unsigned int speed;
u8 fid, vid;

- powernow_table = kzalloc((sizeof(*powernow_table) *
- (number_scales + 1)), GFP_KERNEL);
+ powernow_table = kcalloc(number_scales + 1, sizeof(*powernow_table),
+ GFP_KERNEL);
if (!powernow_table)
return -ENOMEM;

--
2.25.1

2021-09-06 17:09:36

by Rafael J. Wysocki

Subject: Re: [PATCH] cpufreq: powernow: Prefer kcalloc over open coded arithmetic

On Sat, Sep 4, 2021 at 5:16 PM Len Baker <[email protected]> wrote:
>
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, use the purpose specific kcalloc() function instead of the argument
> size * count in the kzalloc() function.
>
> [1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <[email protected]>

I'm assuming that this patch will be picked up by the powerpc arch maintainers.

> ---
> drivers/cpufreq/powernow-k7.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/powernow-k7.c b/drivers/cpufreq/powernow-k7.c
> index 5d515fc34836..a9d2c7bae235 100644
> --- a/drivers/cpufreq/powernow-k7.c
> +++ b/drivers/cpufreq/powernow-k7.c
> @@ -174,8 +174,8 @@ static int get_ranges(unsigned char *pst)
> unsigned int speed;
> u8 fid, vid;
>
> - powernow_table = kzalloc((sizeof(*powernow_table) *
> - (number_scales + 1)), GFP_KERNEL);
> + powernow_table = kcalloc(number_scales + 1, sizeof(*powernow_table),
> + GFP_KERNEL);
> if (!powernow_table)
> return -ENOMEM;
>
> --
> 2.25.1
>