CVE-2021-47450

2024-05-2207:15:10

416baaa9-dc9f-4396-8d5f-8c081fb06d67

web.nvd.nist.gov

linux kernel

kvm

vulnerability

arm64

page-table

refcount

compound page

page-table corruption

hyp_split_page

el2

allocator

nvd

6.6 Medium

AI Score

Confidence

Low

0.0004 Low

EPSS

Percentile

9.1%

JSON

In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: Fix host stage-2 PGD refcount

The KVM page-table library refcounts the pages of concatenated stage-2
PGDs individually. However, when running KVM in protected mode, the
host’s stage-2 PGD is currently managed by EL2 as a single high-order
compound page, which can cause the refcount of the tail pages to reach 0
when they shouldn’t, hence corrupting the page-table.

Fix this by introducing a new hyp_split_page() helper in the EL2 page
allocator (matching the kernel’s split_page() function), and make use of
it from host_s2_zalloc_pages_exact().

Affected configurations

Vulners

Node

linuxlinux_kernelRange5.13–5.14.15

linuxlinux_kernelRange5.15.0≥

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "arch/arm64/kvm/hyp/include/nvhe/gfp.h",
      "arch/arm64/kvm/hyp/nvhe/mem_protect.c",
      "arch/arm64/kvm/hyp/nvhe/page_alloc.c"
    ],
    "versions": [
      {
        "version": "1025c8c0c6ac",
        "lessThan": "b372264c66ef",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1025c8c0c6ac",
        "lessThan": "1d58a17ef545",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "arch/arm64/kvm/hyp/include/nvhe/gfp.h",
      "arch/arm64/kvm/hyp/nvhe/mem_protect.c",
      "arch/arm64/kvm/hyp/nvhe/page_alloc.c"
    ],
    "versions": [
      {
        "version": "5.13",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "5.13",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.14.15",
        "lessThanOrEqual": "5.14.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]