CVE-2022-48700 vfio/type1: Unpin zero pages

2024-05-0315:12:16

Linux

www.cve.org

linux kernel

vulnerability

zero page

pin_user_pages_remote

reference count.

6.5 Medium

AI Score

Confidence

Low

0.0004 Low

EPSS

Percentile

15.8%

JSON

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

vfio/type1: Unpin zero pages

There’s currently a reference count leak on the zero page. We increment
the reference via pin_user_pages_remote(), but the page is later handled
as an invalid/reserved page, therefore it’s not accounted against the
user and not unpinned by our put_pfn().

Introducing special zero page handling in put_pfn() would resolve the
leak, but without accounting of the zero page, a single user could
still create enough mappings to generate a reference count overflow.

The zero page is always resident, so for our purposes there’s no reason
to keep it pinned. Therefore, add a loop to walk pages returned from
pin_user_pages_remote() and unpin any zero pages.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "drivers/vfio/vfio_iommu_type1.c"
    ],
    "versions": [
      {
        "version": "1da177e4c3f4",
        "lessThan": "578d644edc7d",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "5321908ef74f",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "5d721bf22293",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "873aefb376bb",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "drivers/vfio/vfio_iommu_type1.c"
    ],
    "versions": [
      {
        "version": "5.10.146",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.68",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.19.9",
        "lessThanOrEqual": "5.19.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.0",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]