linux-kernel - Re: [PATCH v9 3/6] KVM: arm64: Block cacheable PFNMAP mapping

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Message-ID: <9c45c671-9330-493f-9a8b-2c08062ea0f9@redhat.com>
Date: Fri, 4 Jul 2025 16:09:26 +0200
From: David Hildenbrand <david@...hat.com>
To: ankita@...dia.com, jgg@...dia.com, maz@...nel.org,
 oliver.upton@...ux.dev, joey.gouly@....com, suzuki.poulose@....com,
 yuzenghui@...wei.com, catalin.marinas@....com, will@...nel.org,
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Cc: aniketa@...dia.com, cjia@...dia.com, kwankhede@...dia.com,
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Subject: Re: [PATCH v9 3/6] KVM: arm64: Block cacheable PFNMAP mapping

On 21.06.25 06:21, ankita@...dia.com wrote:
> From: Ankit Agrawal <ankita@...dia.com>
> 
> Fixes a security bug due to mismatched attributes between S1 and
> S2 mapping.
> 
> Currently, it is possible for a region to be cacheable in the userspace
> VMA, but mapped non cached in S2. This creates a potential issue where
> the VMM may sanitize cacheable memory across VMs using cacheable stores,
> ensuring it is zeroed. However, if KVM subsequently assigns this memory
> to a VM as uncached, the VM could end up accessing stale, non-zeroed data
> from a previous VM, leading to unintended data exposure. This is a security
> risk.
> 
> Block such mismatch attributes case by returning EINVAL when userspace
> try to map PFNMAP cacheable. Only allow NORMAL_NC and DEVICE_*.
> 
> CC: Oliver Upton <oliver.upton@...ux.dev>
> CC: Catalin Marinas <catalin.marinas@....com>
> CC: Sean Christopherson <seanjc@...gle.com>
> Suggested-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Ankit Agrawal <ankita@...dia.com>
> ---

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb