CVE-2021-47004 (GCVE-0-2021-47004)

Vulnerability from cvelistv5 – Published: 2024-02-28 08:13 – Updated: 2026-08-05 08:45
VLAI
Title
f2fs: fix to avoid touching checkpointed data in get_victim()
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid touching checkpointed data in get_victim() In CP disabling mode, there are two issues when using LFS or SSR | AT_SSR mode to select victim: 1. LFS is set to find source section during GC, the victim should have no checkpointed data, since after GC, section could not be set free for reuse. Previously, we only check valid chpt blocks in current segment rather than section, fix it. 2. SSR | AT_SSR are set to find target segment for writes which can be fully filled by checkpointed and newly written blocks, we should never select such segment, otherwise it can cause panic or data corruption during allocation, potential case is described as below: a) target segment has 'n' (n < 512) ckpt valid blocks b) GC migrates 'n' valid blocks to other segment (segment is still in dirty list) c) GC migrates '512 - n' blocks to target segment (segment has 'n' cp_vblocks and '512 - n' vblocks) d) If GC selects target segment via {AT,}SSR allocator, however there is no free space in targe segment.
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-09-10 15:58 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 4354994f097d068a894aa1a0860da54571df3582 , < 105155a8146ddb54c119d8318964eef3859d109d (git)
Affected: 4354994f097d068a894aa1a0860da54571df3582 , < 1e116f87825f01a6380286472196882746b16f63 (git)
Affected: 4354994f097d068a894aa1a0860da54571df3582 , < 211372b2571520e394b56b431a0705586013b3ff (git)
Affected: 4354994f097d068a894aa1a0860da54571df3582 , < 61461fc921b756ae16e64243f72af2bfc2e620db (git)
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Linux Linux Affected: 4.20
Unaffected: 0 , < 4.20 (semver)
Unaffected: 5.10.38 , ≤ 5.10.* (semver)
Unaffected: 5.11.22 , ≤ 5.11.* (semver)
Unaffected: 5.12.5 , ≤ 5.12.* (semver)
Unaffected: 5.13 , ≤ * (original_commit_for_fix)
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LFS est\u00e1 configurado para buscar la secci\u00f3n de origen durante la GC, la v\u00edctima no debe tener datos de puntos de control, ya que despu\u00e9s de la GC, la secci\u00f3n no se puede liberar para su reutilizaci\u00f3n. Anteriormente, solo verific\u00e1bamos los bloques chpt v\u00e1lidos en el segmento actual en lugar de en la secci\u00f3n, lo arreglamos. 2. RSS | AT_SSR est\u00e1 configurado para encontrar un segmento de destino para escrituras que se puede llenar completamente con bloques reci\u00e9n escritos y con puntos de control. Nunca debemos seleccionar dicho segmento; de lo contrario, puede causar p\u00e1nico o corrupci\u00f3n de datos durante la asignaci\u00f3n. El caso potencial se describe a continuaci\u00f3n: a) segmento de destino tiene \u0027n\u0027 (n \u0026lt; 512) ckpt bloques v\u00e1lidos b) GC migra \u0027n\u0027 bloques v\u00e1lidos a otro segmento (el segmento todav\u00eda est\u00e1 en la lista sucia) c) GC migra \u0027512 - n\u0027 bloques al segmento objetivo (el segmento tiene \u0027n \u0027 cp_vblocks y \u0027512 - n\u0027 vblocks) d) Si GC selecciona el segmento de destino mediante el asignador {AT,}SSR, sin embargo, no hay espacio libre en el segmento de 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-04T20:05:51+00:00",
      "cve": "CVE-2021-47004",
      "id": "CVE-2021-47004",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:known_affected": "42",
      "product_status:known_not_affected": "156",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: f2fs: fix to avoid touching checkpointed data in get_victim()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47004.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-07-25T17:36:40Z",
      "cve": "CVE-2021-47004",
      "id": "CVE-2021-47004",
      "initial_release_date": "2024-03-01T04:07:57Z",
      "product_status:known_not_affected": "292",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2021-47004",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2021-47004.json",
      "version": "17"
    },
    "vulnrichment": {
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success does not depend on a race or other attacker-uncontrollable conditions.\\nPR:L - Mounting with checkpoint=disable is an admin/deployment precondition, but once that mode is active any unprivileged user with write access triggers the vulnerable get_victim/SSR path through ordinary writes without CAP_SYS_ADMIN.\\nUI:N - Exploitation requires only the attacker\\u2019s own writes on an already checkpoint-disabled f2fs mount; no separate victim interaction is required.\\nS:U - Impact is confined to the local kernel/filesystem authority (panic and filesystem corruption); it does not cross a VM, IOMMU, or other security boundary.\\nC:N - The failure is a logic/allocation bug that panics or corrupts filesystem metadata (summary/SIT/block placement); it does not provide an information-disclosure or arbitrary-read primitive.\\nI:H - Selecting a full segment for SSR can corrupt on-disk data and metadata during allocation (wrong block reuse and summary/journal corruption), which the fix commit explicitly describes as data corruption.\\nA:H - Allocation with next_blkoff \u003e= blocks_per_seg hits f2fs_bug_on (BUG_ON under CONFIG_F2FS_CHECK_FS, otherwise WARN and continued broken state), causing kernel oops/panic or filesystem failure.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"4354994f097d068a894aa1a0860da54571df3582\", \"lessThan\": \"105155a8146ddb54c119d8318964eef3859d109d\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"4354994f097d068a894aa1a0860da54571df3582\", \"lessThan\": \"1e116f87825f01a6380286472196882746b16f63\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"4354994f097d068a894aa1a0860da54571df3582\", \"lessThan\": \"211372b2571520e394b56b431a0705586013b3ff\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"4354994f097d068a894aa1a0860da54571df3582\", \"lessThan\": \"61461fc921b756ae16e64243f72af2bfc2e620db\", \"versionType\": \"git\"}], \"programFiles\": [\"fs/f2fs/f2fs.h\", \"fs/f2fs/gc.c\", \"fs/f2fs/segment.c\", \"fs/f2fs/segment.h\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"4.20\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"4.20\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.10.38\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.11.22\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.11.*\"}, {\"status\": \"unaffected\", \"version\": \"5.12.5\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.12.*\"}, {\"status\": \"unaffected\", \"version\": \"5.13\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"fs/f2fs/f2fs.h\", \"fs/f2fs/gc.c\", \"fs/f2fs/segment.c\", \"fs/f2fs/segment.h\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/105155a8146ddb54c119d8318964eef3859d109d\"}, {\"url\": \"https://git.kernel.org/stable/c/1e116f87825f01a6380286472196882746b16f63\"}, {\"url\": \"https://git.kernel.org/stable/c/211372b2571520e394b56b431a0705586013b3ff\"}, {\"url\": \"https://git.kernel.org/stable/c/61461fc921b756ae16e64243f72af2bfc2e620db\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nf2fs: fix to avoid touching checkpointed data in get_victim()\\n\\nIn CP disabling mode, there are two issues when using LFS or SSR | AT_SSR\\nmode to select victim:\\n\\n1. LFS is set to find source section during GC, the victim should have\\nno checkpointed data, since after GC, section could not be set free for\\nreuse.\\n\\nPreviously, we only check valid chpt blocks in current segment rather\\nthan section, fix it.\\n\\n2. SSR | AT_SSR are set to find target segment for writes which can be\\nfully filled by checkpointed and newly written blocks, we should never\\nselect such segment, otherwise it can cause panic or data corruption\\nduring allocation, potential case is described as below:\\n\\n a) target segment has \u0027n\u0027 (n \u003c 512) ckpt valid blocks\\n b) GC migrates \u0027n\u0027 valid blocks to other segment (segment is still\\n    in dirty list)\\n c) GC migrates \u0027512 - n\u0027 blocks to target segment (segment has \u0027n\u0027\\n    cp_vblocks and \u0027512 - n\u0027 vblocks)\\n d) If GC selects target segment via {AT,}SSR allocator, however there\\n    is no free space in targe segment.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.38\", \"versionStartIncluding\": \"4.20\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.11.22\", \"versionStartIncluding\": \"4.20\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.12.5\", \"versionStartIncluding\": \"4.20\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.13\", \"versionStartIncluding\": \"4.20\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T08:45:31.112Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47004\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T08:45:31.112Z\", \"dateReserved\": \"2024-02-27T18:42:55.951Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-02-28T08:13:25.324Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.