linux-hardening - Re: [PATCH] i3c/master/mipi-i3c-hci: Prefer kcalloc over open coded arithmetic

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Message-ID: <0611r11-rsq7-2n9-n834-9o31rq8qo737@onlyvoer.pbz>
Date:   Sun, 12 Sep 2021 21:54:00 -0400 (EDT)
From:   Nicolas Pitre <npitre@...libre.com>
To:     Len Baker <len.baker@....com>
cc:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Kees Cook <keescook@...omium.org>,
        linux-i3c@...ts.infradead.org, linux-hardening@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i3c/master/mipi-i3c-hci: Prefer kcalloc over open coded
 arithmetic

On Sun, 12 Sep 2021, Len Baker 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@....com>

Acked-by: Nicolas Pitre <npitre@...libre.com>

> ---
>  drivers/i3c/master/mipi-i3c-hci/hci.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i3c/master/mipi-i3c-hci/hci.h b/drivers/i3c/master/mipi-i3c-hci/hci.h
> index 80beb1d5be8f..f109923f6c3f 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/hci.h
> +++ b/drivers/i3c/master/mipi-i3c-hci/hci.h
> @@ -98,7 +98,7 @@ struct hci_xfer {
> 
>  static inline struct hci_xfer *hci_alloc_xfer(unsigned int n)
>  {
> -	return kzalloc(sizeof(struct hci_xfer) * n, GFP_KERNEL);
> +	return kcalloc(n, sizeof(struct hci_xfer), GFP_KERNEL);
>  }
> 
>  static inline void hci_free_xfer(struct hci_xfer *xfer, unsigned int n)
> --
> 2.25.1
> 
>