linux-hardening - Re: [PATCH v2] dmaengine: pl08x: Use kcalloc() instead of kzalloc()

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Date: Sun, 7 Apr 2024 17:09:39 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Erick Archer <erick.archer@...look.com>
Cc: Kees Cook <keescook@...omium.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] dmaengine: pl08x: Use kcalloc() instead of kzalloc()

On 30-03-24, 16:23, Erick Archer wrote:
> This is an effort to get rid of all multiplications from allocation
> functions in order to prevent integer overflows [1].
> 
> Here the multiplication is obviously safe because the "channels"
> member can only be 8 or 2. This value is set when the "vendor_data"
> structs are initialized.
> 
> static struct vendor_data vendor_pl080 = {
> 	[...]
> 	.channels = 8,
> 	[...]
> };
> 
> static struct vendor_data vendor_nomadik = {
> 	[...]
> 	.channels = 8,
> 	[...]
> };
> 
> static struct vendor_data vendor_pl080s = {
> 	[...]
> 	.channels = 8,
> 	[...]
> };
> 
> static struct vendor_data vendor_pl081 = {
> 	[...]
> 	.channels = 2,
> 	[...]
> };
> 
> However, using kcalloc() is more appropriate [1] and improves
> readability. This patch has no effect on runtime behavior.
> 
> Link: https://github.com/KSPP/linux/issues/162 [1]
> Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
> Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> Signed-off-by: Erick Archer <erick.archer@...look.com>
> ---
> Changes in v2:
> - Add the "Reviewed-by:" tag.
> - Rebase against linux-next.
> 
> Previous versions:
> v1 -> https://lore.kernel.org/linux-hardening/20240128115236.4791-1-erick.archer@gmx.com/
> 
> Hi everyone,
> 
> This patch seems to be lost. Gustavo reviewed it on January 30, 2024
> but the patch has not been applied since.
> 
> Thanks,
> Erick
> ---
>  drivers/dma/amba-pl08x.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
> index fbf048f432bf..73a5cfb4da8a 100644
> --- a/drivers/dma/amba-pl08x.c
> +++ b/drivers/dma/amba-pl08x.c
> @@ -2855,8 +2855,8 @@ static int pl08x_probe(struct amba_device *adev, const struct amba_id *id)
>  	}
>  
>  	/* Initialize physical channels */
> -	pl08x->phy_chans = kzalloc((vd->channels * sizeof(*pl08x->phy_chans)),
> -			GFP_KERNEL);
> +	pl08x->phy_chans = kcalloc(vd->channels, sizeof(*pl08x->phy_chans),
> +				   GFP_KERNEL);

How is one better than the other?


>  	if (!pl08x->phy_chans) {
>  		ret = -ENOMEM;
>  		goto out_no_phychans;
> -- 
> 2.25.1

-- 
~Vinod