linux-kernel - Re: [PATCH 2/2] iommu: add Unisoc iommu basic driver

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Date:   Tue, 2 Feb 2021 15:13:50 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Chunyan Zhang <zhang.lyra@...il.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        Rob Herring <robh+dt@...nel.org>,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        Baolin Wang <baolin.wang7@...il.com>,
        linux-kernel@...r.kernel.org, Orson Zhai <orsonzhai@...il.com>,
        Sheng Xu <sheng.xu@...soc.com>,
        Chunyan Zhang <chunyan.zhang@...soc.com>
Subject: Re: [PATCH 2/2] iommu: add Unisoc iommu basic driver

On Tue, Feb 02, 2021 at 06:42:57PM +0800, Chunyan Zhang wrote:
> +static phys_addr_t sprd_iommu_iova_to_phys(struct iommu_domain *domain,
> +					   dma_addr_t iova)
> +{
> +	struct sprd_iommu_domain *dom = to_sprd_domain(domain);
> +	unsigned long flags;
> +	phys_addr_t pa;
> +	unsigned long start = domain->geometry.aperture_start;
> +	unsigned long end = domain->geometry.aperture_end;
> +
> +	if (iova < start || iova > end)
> +		pr_err("iova (0x%llx) exceed the vpn range[0x%lx-0x%lx]!\n",
> +		       iova, start, end);

It is not a good idea to continue here with an out-of-range iova. The
code below might access random memory for its checks. Better do a
WARN_ON here and return an invalid physical address.

> +
> +	spin_lock_irqsave(&dom->pgtlock, flags);
> +	pa = *(dom->pgt_va + ((iova - start) >> SPRD_IOMMU_PAGE_SHIFT));
> +	pa = (pa << SPRD_IOMMU_PAGE_SHIFT) + ((iova - start) & (SPRD_IOMMU_PAGE_SIZE - 1));
> +	spin_unlock_irqrestore(&dom->pgtlock, flags);
> +
> +	return pa;
> +}
> +