CVE-2021-46990 (GCVE-0-2021-46990)

Vulnerability from cvelistv5 – Published: 2024-02-28 08:13 – Updated: 2026-05-23 15:18
VLAI
Title
powerpc/64s: Fix crashes when toggling entry flush barrier
Summary
In the Linux kernel, the following vulnerability has been resolved: powerpc/64s: Fix crashes when toggling entry flush barrier The entry flush mitigation can be enabled/disabled at runtime via a debugfs file (entry_flush), which causes the kernel to patch itself to enable/disable the relevant mitigations. However depending on which mitigation we're using, it may not be safe to do that patching while other CPUs are active. For example the following crash: sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20 Shows that we returned to userspace with a corrupted LR that points into the kernel, due to executing the partially patched call to the fallback entry flush (ie. we missed the LR restore). Fix it by doing the patching under stop machine. The CPUs that aren't doing the patching will be spinning in the core of the stop machine logic. That is currently sufficient for our purposes, because none of the patching we do is to that code or anywhere in the vicinity.
Severity
No CVSS data available.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 4a1e90af718d1489ffcecc8f52486c4f5dc0f7a6 , < 8382b15864e5014261b4f36c2aa89723612ee058 (git)
Affected: fa4bf9f38184ed7ca4916eb64f8c767d1e279c1f , < 0c25a7bb697f2e6ee65b6d63782f675bf129511a (git)
Affected: db01cad9efe3c3838a6b3a3f68affd295c4b92d6 , < ee4b7aab93c2631c3bb0753023c5dda592bb666b (git)
Affected: f69bb4e51f41973fb7594be1479fa689831efe1a , < 2db22ba4e0e103f00e0512e0ecce36ac78c644f8 (git)
Affected: b65458b6be8032c5179d4f562038575d7b3a6be3 , < 0b4eb172cc12dc102cd0ad013e53ee4463db9508 (git)
Affected: f79643787e0a0762d2409b7b8334e83f22d85695 , < d2e3590ca39ccfd8a5a46d8c7f095cb6c7b9ae92 (git)
Affected: f79643787e0a0762d2409b7b8334e83f22d85695 , < dd0d6117052faace5440db20fc37175efe921c7d (git)
Affected: f79643787e0a0762d2409b7b8334e83f22d85695 , < 5bc00fdda1e934c557351a9c751a205293e68cbf (git)
Affected: f79643787e0a0762d2409b7b8334e83f22d85695 , < aec86b052df6541cc97c5fca44e5934cbea4963b (git)
Affected: e590b36718d6e740b7b19514f710402a6499164c (git)
Affected: 4.4.245 , < 4.4.269 (semver)
Affected: 4.9.245 , < 4.9.269 (semver)
Affected: 4.14.208 , < 4.14.233 (semver)
Affected: 4.19.159 , < 4.19.191 (semver)
Affected: 5.4.79 , < 5.4.120 (semver)
Affected: 5.9.10 , < 5.10 (semver)
Create a notification for this product.
Linux Linux Affected: 5.10
Unaffected: 0 , < 5.10 (semver)
Unaffected: 4.4.269 , ≤ 4.4.* (semver)
Unaffected: 4.9.269 , ≤ 4.9.* (semver)
Unaffected: 4.14.233 , ≤ 4.14.* (semver)
Unaffected: 4.19.191 , ≤ 4.19.* (semver)
Unaffected: 5.4.120 , ≤ 5.4.* (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)
Create a notification for this product.
Show details on NVD website
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      "lastModified": "2024-12-26T15:01:41.753",
      "metrics": "{\"cvssMetricV31\": [{\"source\": \"nvd@nist.gov\", \"type\": \"Primary\", \"cvssData\": {\"version\": \"3.1\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H\", \"baseScore\": 5.5, \"baseSeverity\": \"MEDIUM\", \"attackVector\": \"LOCAL\", \"attackComplexity\": \"LOW\", \"privilegesRequired\": \"LOW\", \"userInteraction\": \"NONE\", \"scope\": \"UNCHANGED\", \"confidentialityImpact\": \"NONE\", \"integrityImpact\": \"NONE\", \"availabilityImpact\": \"HIGH\"}, \"exploitabilityScore\": 1.8, \"impactScore\": 3.6}]}",
      "published": "2024-02-28T09:15:37.733",
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      "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "vulnStatus": "Analyzed",
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For example the following\\ncrash:\\n\\n  sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20\\n\\nShows that we returned to userspace with a corrupted LR that points into\\nthe kernel, due to executing the partially patched call to the fallback\\nentry flush (ie. we missed the LR restore).\\n\\nFix it by doing the patching under stop machine. The CPUs that aren\u0027t\\ndoing the patching will be spinning in the core of the stop machine\\nlogic. That is currently sufficient for our purposes, because none of\\nthe patching we do is to that code or anywhere in the vicinity.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: powerpc/64s: soluciona fallas al alternar la barrera de descarga de entrada. 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    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2025-11-21T14:11:24+00:00",
      "cve": "CVE-2021-46990",
      "id": "CVE-2021-46990",
      "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: powerpc/64s: Fix crashes when toggling entry flush barrier",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-46990.json",
      "version": "3"
    },
    "vulnrichment": {
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      "cveMetadata": "{\"cveId\": \"CVE-2021-46990\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-23T15:18:54.715Z\", \"dateReserved\": \"2024-02-27T18:42:55.948Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-02-28T08:13:16.569Z\", \"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

Author Source Type Date Other

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.