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mm: swap: fix race between free_swap_and_cache() and swapoff()

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: mm: swap: fix race between free_swap_and_cache() and swapoff() There was previously a theoretical window where swapoff() could run and teardown a swap_info_struct while a call to free_swap_and_cache() was running in another thread. This could cause, amongst other bad possibilities, swap_page_trans_huge_swapped() (called by free_swap_and_cache()) to access the freed memory for swap_map. This is a theoretical problem and I haven't been able to provoke it from a test case. But there has been agreement based on code review that this is possible (see link below). Fix it by using get_swap_device()/put_swap_device(), which will stall swapoff(). There was an extra check in _swap_info_get() to confirm that the swap entry was not free. This isn't present in get_swap_device() because it doesn't make sense in general due to the race between getting the reference and swapoff. So I've added an equivalent check directly in free_swap_and_cache(). Details of how to provoke one possible issue (thanks to David Hildenbrand for deriving this): --8<----- __swap_entry_free() might be the last user and result in "count == SWAP_HAS_CACHE". swapoff->try_to_unuse() will stop as soon as soon as si->inuse_pages==0. So the question is: could someone reclaim the folio and turn si->inuse_pages==0, before we completed swap_page_trans_huge_swapped(). Imagine the following: 2 MiB folio in the swapcache. Only 2 subpages are still references by

Announced Source revision 1
Original source ↗

CVE-2024-26960

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2024-26960

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "7c00bafee87c7bac7ed9eced7c161f8e5332cb4e",
        "lessThan": "d85c11c97ecf92d47a4b29e3faca714dc1f18d0d",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7c00bafee87c7bac7ed9eced7c161f8e5332cb4e",
        "lessThan": "2da5568ee222ce0541bfe446a07998f92ed1643e",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7c00bafee87c7bac7ed9eced7c161f8e5332cb4e",
        "lessThan": "1ede7f1d7eed1738d1b9333fd1e152ccb450b86a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7c00bafee87c7bac7ed9eced7c161f8e5332cb4e",
        "lessThan": "0f98f6d2fb5fad00f8299b84b85b6bc1b6d7d19a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7c00bafee87c7bac7ed9eced7c161f8e5332cb4e",
        "lessThan": "3ce4c4c653e4e478ecb15d3c88e690f12cbf6b39",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7c00bafee87c7bac7ed9eced7c161f8e5332cb4e",
        "lessThan": "363d17e7f7907c8e27a9e86968af0eaa2301787b",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "7c00bafee87c7bac7ed9eced7c161f8e5332cb4e",
        "lessThan": "82b1c07a0af603e3c47b906c8e991dc96f01688e",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "mm/swapfile.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "4.11"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "4.11",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.215",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.154",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.84",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.24",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.7.12",
        "versionType": "semver",
        "lessThanOrEqual": "6.7.*"
      },
      {
        "status": "unaffected",
        "version": "6.8.3",
        "versionType": "semver",
        "lessThanOrEqual": "6.8.*"
      },
      {
        "status": "unaffected",
        "version": "6.9",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "mm/swapfile.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2024-26960

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#26468 · Revision 1
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Publisher date
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