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* [PATCH] cpufreq: powernow: Prefer kcalloc over open coded arithmetic
@ 2021-09-04 15:16 Len Baker
  2021-09-06 17:05 ` Rafael J. Wysocki
  0 siblings, 1 reply; 2+ messages in thread
From: Len Baker @ 2021-09-04 15:16 UTC (permalink / raw)
  To: Rafael J. Wysocki, Viresh Kumar
  Cc: Len Baker, Kees Cook, linux-pm, linux-hardening, linux-kernel

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 <len.baker@gmx.com>
---
 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


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] cpufreq: powernow: Prefer kcalloc over open coded arithmetic
  2021-09-04 15:16 [PATCH] cpufreq: powernow: Prefer kcalloc over open coded arithmetic Len Baker
@ 2021-09-06 17:05 ` Rafael J. Wysocki
  0 siblings, 0 replies; 2+ messages in thread
From: Rafael J. Wysocki @ 2021-09-06 17:05 UTC (permalink / raw)
  To: Len Baker
  Cc: Rafael J. Wysocki, Viresh Kumar, Kees Cook, Linux PM,
	linux-hardening, Linux Kernel Mailing List

On Sat, Sep 4, 2021 at 5:16 PM Len Baker <len.baker@gmx.com> 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 <len.baker@gmx.com>

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
>

^ permalink raw reply	[flat|nested] 2+ messages in thread

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