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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Jun 2025 04:21:18.1645 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 67d95c7a-d3f9-458e-f9f7-08ddb07b11c1 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.233];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SJ5PEPF000001E9.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB6168 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250620_212129_409317_20955EEE X-CRM114-Status: GOOD ( 15.83 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 5fe24f30999d..68c0f1c25dec 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1465,6 +1465,22 @@ static bool kvm_vma_mte_allowed(struct vm_area_struct *vma) return vma->vm_flags & VM_MTE_ALLOWED; } +/* + * Determine the memory region cacheability from VMA's pgprot. This + * is used to set the stage 2 PTEs. + */ +static bool kvm_vma_is_cacheable(struct vm_area_struct *vma) +{ + switch (FIELD_GET(PTE_ATTRINDX_MASK, pgprot_val(vma->vm_page_prot))) { + case MT_NORMAL_NC: + case MT_DEVICE_nGnRnE: + case MT_DEVICE_nGnRE: + return false; + default: + return true; + } +} + static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, struct kvm_s2_trans *nested, struct kvm_memory_slot *memslot, unsigned long hva, @@ -1472,7 +1488,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, { int ret = 0; bool write_fault, writable, force_pte = false; - bool exec_fault, mte_allowed; + bool exec_fault, mte_allowed, is_vma_cacheable; bool s2_force_noncacheable = false, vfio_allow_any_uc = false; unsigned long mmu_seq; phys_addr_t ipa = fault_ipa; @@ -1617,6 +1633,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, vm_flags = vma->vm_flags; + is_vma_cacheable = kvm_vma_is_cacheable(vma); + /* Don't use the VMA after the unlock -- it may have vanished */ vma = NULL; @@ -1660,6 +1678,14 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, writable = false; } + /* + * Prohibit a region to be mapped non cacheable in S2 and marked as + * cacheabled in the userspace VMA. Such mismatched mapping is a + * security risk. + */ + if (is_vma_cacheable && s2_force_noncacheable) + return -EINVAL; + if (exec_fault && s2_force_noncacheable) return -ENOEXEC; @@ -2219,6 +2245,12 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, ret = -EINVAL; break; } + + /* Cacheable PFNMAP is not allowed */ + if (kvm_vma_is_cacheable(vma)) { + ret = -EINVAL; + break; + } } hva = min(reg_end, vma->vm_end); } while (hva < reg_end); -- 2.34.1