linux-hardening - Re: [PATCH v3] docs: deprecated.rst: Clarify open-coded arithmetic with literals

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Date:   Wed, 20 Oct 2021 18:52:14 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Len Baker <len.baker@....com>
Cc:     Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Joe Perches <joe@...ches.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3] docs: deprecated.rst: Clarify open-coded arithmetic
 with literals

On Sat, Sep 25, 2021 at 04:34:55PM +0200, Len Baker wrote:
> Although using literals for size calculation in allocator arguments may
> be harmless due to compiler warnings in case of overflows, it is better
> to refactor the code to avoid the use of open-coded arithmetic.
> 
> So, clarify the preferred way in these cases.
> 
> Suggested-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Len Baker <len.baker@....com>

This looks good to me.

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks
--
Gustavo

> ---
> Changelog v1 -> v2
>  - Clarify the sentence by changing "keep <foo> out" with "avoid <foo>"
>    (Joe Perches).
> 
> Changelog v2 -> v3
>  - Reword the sentence to comunicate better (Jonathan Corbet).
> 
> The previous version can be found here [1].
> 
> [1] https://lore.kernel.org/linux-hardening/20210829144716.2931-1-len.baker@gmx.com/
> 
>  Documentation/process/deprecated.rst | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
> index 8ced754a5a0f..388cb19f5dbb 100644
> --- a/Documentation/process/deprecated.rst
> +++ b/Documentation/process/deprecated.rst
> @@ -59,8 +59,9 @@ 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. (One exception to this is literal values where the compiler
> -can warn if they might overflow. Though using literals for arguments as
> -suggested below is also harmless.)
> +can warn if they might overflow. However, the preferred way in these
> +cases is to refactor the code as suggested below to avoid the open-coded
> +arithmetic.)
> 
>  For example, do not use ``count * size`` as an argument, as in::
> 
> --
> 2.25.1
>