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b=tXym3Q84Zf5oFf0O8EIrMHuqj8aZsOo5LS+tasIcYOyNV1khV4muUgzsIgJhypT36 LLxDOmfCdp6MIbkQDAnE1hcu7PbIR0VP7FdZsnBfmnQ4Xqo4NYv9iCMS08w1+bVDxr yuNxbf2j+dHfJpPSA04KrChBV4Xn62IrSg945Ia0hLhO41fapaoHJmX0IRs+2u4NE3 cPAv+OaowQcbaQgJc6Phkf8ZvLtmgvSK8UUmB7GNUOFN5pzKsefuYrgYP6vpfXqV4m OpPp7UlHxPHT7TfN1DGpsNUCACNbloluxbWOaIHkZNQ2pQWlTwp1s9gZXE54ndx3mT v5m+3RqiBEbpA== Date: Fri, 27 Jun 2025 14:49:30 +0100 From: Will Deacon To: ankita@nvidia.com Cc: jgg@nvidia.com, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, ryan.roberts@arm.com, shahuang@redhat.com, lpieralisi@kernel.org, david@redhat.com, ddutile@redhat.com, seanjc@google.com, aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, kjaju@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, zhiw@nvidia.com, mochs@nvidia.com, udhoke@nvidia.com, dnigam@nvidia.com, alex.williamson@redhat.com, sebastianene@google.com, coltonlewis@google.com, kevin.tian@intel.com, yi.l.liu@intel.com, ardb@kernel.org, akpm@linux-foundation.org, gshan@redhat.com, linux-mm@kvack.org, tabba@google.com, qperret@google.com, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, maobibo@loongson.cn, pbonzini@redhat.com Subject: Re: [PATCH v9 3/6] KVM: arm64: Block cacheable PFNMAP mapping Message-ID: References: <20250621042111.3992-1-ankita@nvidia.com> <20250621042111.3992-4-ankita@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250621042111.3992-4-ankita@nvidia.com> X-Rspamd-Server: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: B2A091C0009 X-Stat-Signature: 7a1np7gs4h5kuukmcnsnegfdz35qnh1g X-HE-Tag: 1751032182-272767 X-HE-Meta: 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 tx5fIpWp RpyIGJdey36rf4LxJ7Edi3B3Kz92+ddYh6dMRvuLP6joOP5cxU1AatlBxJUTVJ5raX9gbPCvsLTW36Puy5jhQIVm06wxJ8J8kOdZ3uBz1vcBCx/RZWhQ9pZYr1oK6ft0njb7mSb2lzl6B7y7h1vLe5iBbDfXN1ogHwSiMbvZYafSNQGz4ZWSCYI8MhigRtOn08hV4tMhBUvAI1feun9W6oCGTZFKzVfOj3tHLX/t/Tsw3LiJ/AOCkpEfXNzSl/ivg8pWoZPh1/fQMtY68iglPBKfNj5blGrxBoyShIuwcF+zuplTDJC3PZsMWq+j1+Z2fe0jmm5YNAVTwzqkN7bVDdVKDbahlc4GK3o0ZUq33C89tBOWq2Mh2NZCpF4xXxJwSMEiaZpAEp48GajL6W+VysFKEug== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Jun 21, 2025 at 04:21:08AM +0000, ankita@nvidia.com wrote: > From: Ankit Agrawal > > 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 > CC: Catalin Marinas > CC: Sean Christopherson > Suggested-by: Jason Gunthorpe > Signed-off-by: Ankit Agrawal > --- > arch/arm64/kvm/mmu.c | 34 +++++++++++++++++++++++++++++++++- > 1 file changed, 33 insertions(+), 1 deletion(-) Sorry for the drive-by comment, but I was looking at this old series from Paolo (look at the cover letter and patch 5): https://lore.kernel.org/r/20250109133817.314401-1-pbonzini@redhat.com in which he points out that the arm64 get_vma_page_shift() function incorrectly assumes that a VM_PFNMAP VMA is physically contiguous, which may not be the case if a driver calls remap_pfn_range() to mess around with mappings within the VMA. I think that implies that the optimisation in 2aa53d68cee6 ("KVM: arm64: Try stage2 block mapping for host device MMIO") is unsound. But it got me thinking -- given that remap_pfn_range() also takes a 'prot' argument, how do we ensure that this is reflected in the guest? It feels a bit dodgy to rely on drivers always passing 'vma->vm_page_prot'. Will