CVE-2024-26630 mm: cachestat: fix folio read-after-free in cache walk

2024-03-1315:50:32

Linux

www.cve.org

cachestat

folio read-after-free

xarray

tmpfs files

dirty and writeback counters

AI Score

6.7

Confidence

Low

EPSS

Percentile

15.5%

JSON

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

mm: cachestat: fix folio read-after-free in cache walk

In cachestat, we access the folio from the page cache’s xarray to compute
its page offset, and check for its dirty and writeback flags. However, we
do not hold a reference to the folio before performing these actions,
which means the folio can concurrently be released and reused as another
folio/page/slab.

Get around this altogether by just using xarray’s existing machinery for
the folio page offsets and dirty/writeback states.

This changes behavior for tmpfs files to now always report zeroes in their
dirty and writeback counters. This is okay as tmpfs doesn’t follow
conventional writeback cache behavior: its pages get “cleaned” during
swapout, after which they’re no longer resident etc.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "mm/filemap.c"
    ],
    "versions": [
      {
        "version": "cf264e1329fb",
        "lessThan": "ba60fdf75e89",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "cf264e1329fb",
        "lessThan": "fe7e008e0ce7",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "cf264e1329fb",
        "lessThan": "3a75cb05d53f",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "mm/filemap.c"
    ],
    "versions": [
      {
        "version": "6.5",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "6.5",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.21",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.7.9",
        "lessThanOrEqual": "6.7.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.8",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]