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From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Len Baker <len.baker@gmx.com>, Daniel Mack <daniel@zonque.org>,
	Haojian Zhuang <haojian.zhuang@gmail.com>,
	Robert Jarzmik <robert.jarzmik@free.fr>,
	Vinod Koul <vkoul@kernel.org>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	linux-arm-kernel@lists.infradead.org, dmaengine@vger.kernel.org,
	linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dmaengine: pxa_dma: Prefer struct_size over open coded arithmetic
Date: Mon, 20 Sep 2021 19:00:58 -0500	[thread overview]
Message-ID: <e7e103f3-74eb-9cf4-a150-e2333d4f2ace@embeddedor.com> (raw)
In-Reply-To: <20210918104055.8444-1-len.baker@gmx.com>



On 9/18/21 05:40, 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 struct_size() helper to do the arithmetic instead of the
> argument "size + count * size" in the kzalloc() function.
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> 
> Signed-off-by: Len Baker <len.baker@gmx.com>

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

> ---
>  drivers/dma/pxa_dma.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c
> index 4a2a796e348c..52d04641e361 100644
> --- a/drivers/dma/pxa_dma.c
> +++ b/drivers/dma/pxa_dma.c
> @@ -742,8 +742,7 @@ pxad_alloc_desc(struct pxad_chan *chan, unsigned int nb_hw_desc)
>  	dma_addr_t dma;
>  	int i;
> 
> -	sw_desc = kzalloc(sizeof(*sw_desc) +
> -			  nb_hw_desc * sizeof(struct pxad_desc_hw *),
> +	sw_desc = kzalloc(struct_size(sw_desc, hw_desc, nb_hw_desc),
>  			  GFP_NOWAIT);
>  	if (!sw_desc)
>  		return NULL;
> --
> 2.25.1
> 

  reply	other threads:[~2021-09-20 23:59 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-18 10:40 Len Baker
2021-09-21  0:00 ` Gustavo A. R. Silva [this message]
2021-10-20 23:32   ` Gustavo A. R. Silva

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