linux-hardening - Re: [PATCH] iommu/vt-d: Use kcalloc() instead of kzalloc()

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Date: Mon, 12 Feb 2024 14:41:38 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Erick Archer <erick.archer@....com>, David Woodhouse
 <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Kees Cook <keescook@...omium.org>
Cc: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH] iommu/vt-d: Use kcalloc() instead of kzalloc()



On 2/11/24 11:51, 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 DMAR_LATENCY_NUM
> is the number of latency types defined in the "latency_type" enum.
> 
> enum latency_type {
> 	DMAR_LATENCY_INV_IOTLB = 0,
> 	DMAR_LATENCY_INV_DEVTLB,
> 	DMAR_LATENCY_INV_IEC,
> 	DMAR_LATENCY_PRQ,
> 	DMAR_LATENCY_NUM
> };
> 
> However, using kcalloc() is more appropriate [2] 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 [2]
> Signed-off-by: Erick Archer <erick.archer@....com>

LGTM:

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

Thanks!
-- 
Gustavo

> ---
>   drivers/iommu/intel/perf.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/intel/perf.c b/drivers/iommu/intel/perf.c
> index 94ee70ac38e3..adc4de6bbd88 100644
> --- a/drivers/iommu/intel/perf.c
> +++ b/drivers/iommu/intel/perf.c
> @@ -33,7 +33,7 @@ int dmar_latency_enable(struct intel_iommu *iommu, enum latency_type type)
> 
>   	spin_lock_irqsave(&latency_lock, flags);
>   	if (!iommu->perf_statistic) {
> -		iommu->perf_statistic = kzalloc(sizeof(*lstat) * DMAR_LATENCY_NUM,
> +		iommu->perf_statistic = kcalloc(DMAR_LATENCY_NUM, sizeof(*lstat),
>   						GFP_ATOMIC);
>   		if (!iommu->perf_statistic) {
>   			ret = -ENOMEM;
> --
> 2.25.1
> 
>