linux-kernel - Re: [PATCH] docs/zh_CN/power: Use kcalloc() instead of kzalloc()

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Date: Sun, 21 Jan 2024 11:02:00 +0100
From: Erick Archer <erick.archer@....com>
To: Hu Haowen <2023002089@...k.tyut.edu.cn>,
	Jonathan Corbet <corbet@....net>
Cc: Erick Archer <erick.archer@....com>, Alex Shi <alexs@...nel.org>,
	Yanteng Si <siyanteng@...ngson.cn>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] docs/zh_CN/power: Use kcalloc() instead of kzalloc()

Hi Hu and Jonathan,

On Sat, Jan 20, 2024 at 10:24:42PM +0800, Hu Haowen wrote:
>
> 在 2024/1/20 20:22, Erick Archer 写道:
> > 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, in the example code use the purpose specific kcalloc() function
> > instead of the argument size * count in the kzalloc() function.
> >
> > Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
> > Link: https://github.com/KSPP/linux/issues/162
> > Signed-off-by: Erick Archer <erick.archer@....com>
> > ---
> >   Documentation/translations/zh_CN/power/opp.rst | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/Documentation/translations/zh_CN/power/opp.rst b/Documentation/translations/zh_CN/power/opp.rst
> > index 8d6e3f6f6202..7470fa2d4c43 100644
> > --- a/Documentation/translations/zh_CN/power/opp.rst
> > +++ b/Documentation/translations/zh_CN/power/opp.rst
> > @@ -274,7 +274,7 @@ dev_pm_opp_get_opp_count
> >   	 {
> >   		/* 做一些事情 */
> >   		num_available = dev_pm_opp_get_opp_count(dev);
> > -		speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL);
> > +		speeds = kcalloc(num_available, sizeof(u32), GFP_KERNEL);
>
>
> If the translated version is modified, I think the original file should
> follow as well at Documentation/power/opp.rst line 308:
>
> diff --git a/Documentation/power/opp.rst b/Documentation/power/opp.rst
> index a7c03c470980..dca35018214a 100644
> --- a/Documentation/power/opp.rst
> +++ b/Documentation/power/opp.rst
> @@ -305,7 +305,7 @@ dev_pm_opp_get_opp_count
>          {
>                 /* Do things */
>                 num_available = dev_pm_opp_get_opp_count(dev);
> -               speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL);
> +               speeds = kcalloc(sizeof(u32) * num_available, GFP_KERNEL);
>                 /* populate the table in increasing order */
>                 freq = 0;
>                 while (!IS_ERR(opp = dev_pm_opp_find_freq_ceil(dev, &freq)))
> {

As you both suggested, this change should be made if the original file is
changed. Therefore, before this patch I already sent another one [1] that
made the proposed changes to the original file.

[1] https://lore.kernel.org/linux-hardening/20240120120527.3866-1-erick.archer@gmx.com/

But if you prefer, I can send just one patch with the two changes.

Best regards,
Erick

>
> Thanks,
> Hu Haowen
>
>
> >   		/* 按升序填充表 */
> >   		freq = 0;
> >   		while (!IS_ERR(opp = dev_pm_opp_find_freq_ceil(dev, &freq))) {
> > --
> > 2.25.1
> >
> >
> >