linux-kernel - Re: [PATCH v2] dmaengine: idxd: Do not enable user type Work Queue without Shared Virtual Addressing

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Message-ID: <Y0/8Y0xUuUoi3KvL@matsya>
Date:   Wed, 19 Oct 2022 19:02:19 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        dmaengine@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH v2] dmaengine: idxd: Do not enable user type Work Queue
 without Shared Virtual Addressing

On 14-10-22, 15:25, Fenghua Yu wrote:
> When the idxd_user_drv driver is bound to a Work Queue (WQ) device
> without IOMMU or with IOMMU Passthrough without Shared Virtual
> Addressing (SVA), the application gains direct access to physical
> memory via the device by programming physical address to a submitted
> descriptor. This allows direct userspace read and write access to
> arbitrary physical memory. This is inconsistent with the security
> goals of a good kernel API.
> 
> Unlike vfio_pci driver, the IDXD char device driver does not provide any
> ways to pin user pages and translate the address from user VA to IOVA or
> PA without IOMMU SVA. Therefore the application has no way to instruct the
> device to perform DMA function. This makes the char device not usable for
> normal application usage.
> 
> Since user type WQ without SVA cannot be used for normal application usage
> and presents the security issue, bind idxd_user_drv driver and enable user
> type WQ only when SVA is enabled (i.e. user PASID is enabled).

Applied, thanks

-- 
~Vinod