linux-kernel - Re: [PATCH 1/2] iommu/arm-smmu-v3: Avoid open coded arithmetic in memory allocation

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Message-ID: <f17da9b7-1642-762c-0854-e131e3c2f438@arm.com>
Date:   Mon, 7 Feb 2022 10:26:15 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Will Deacon <will@...nel.org>, Joerg Roedel <joro@...tes.org>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org
Subject: Re: [PATCH 1/2] iommu/arm-smmu-v3: Avoid open coded arithmetic in
 memory allocation

On 2022-02-05 17:10, Christophe JAILLET wrote:
> kmalloc_array()/kcalloc() should be used to avoid potential overflow when
> a multiplication is needed to compute the size of the requested memory.
> 
> So turn a devm_kzalloc()+explicit size computation into an equivalent
> devm_kcalloc().
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> This is NOT compile tested.
> I don't have the needed cross compiling tools.

FYI, https://cdn.kernel.org/pub/tools/crosstool/

Either way, the patch looks reasonable, thanks!

Acked-by: Robin Murphy <robin.murphy@....com>

> ---
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 6dc6d8b6b368..14d06aad0726 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2981,10 +2981,10 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu)
>   {
>   	unsigned int i;
>   	struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg;
> -	size_t size = sizeof(*cfg->l1_desc) * cfg->num_l1_ents;
>   	void *strtab = smmu->strtab_cfg.strtab;
>   
> -	cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL);
> +	cfg->l1_desc = devm_kcalloc(smmu->dev, cfg->num_l1_ents,
> +				    sizeof(*cfg->l1_desc), GFP_KERNEL);
>   	if (!cfg->l1_desc)
>   		return -ENOMEM;
>