CVE-2021-47189 (GCVE-0-2021-47189)

Vulnerability from cvelistv5 – Published: 2024-04-10 18:56 – Updated: 2026-05-11 13:49
VLAI
Title
btrfs: fix memory ordering between normal and ordered work functions
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix memory ordering between normal and ordered work functions Ordered work functions aren't guaranteed to be handled by the same thread which executed the normal work functions. The only way execution between normal/ordered functions is synchronized is via the WORK_DONE_BIT, unfortunately the used bitops don't guarantee any ordering whatsoever. This manifested as seemingly inexplicable crashes on ARM64, where async_chunk::inode is seen as non-null in async_cow_submit which causes submit_compressed_extents to be called and crash occurs because async_chunk::inode suddenly became NULL. The call trace was similar to: pc : submit_compressed_extents+0x38/0x3d0 lr : async_cow_submit+0x50/0xd0 sp : ffff800015d4bc20 <registers omitted for brevity> Call trace: submit_compressed_extents+0x38/0x3d0 async_cow_submit+0x50/0xd0 run_ordered_work+0xc8/0x280 btrfs_work_helper+0x98/0x250 process_one_work+0x1f0/0x4ac worker_thread+0x188/0x504 kthread+0x110/0x114 ret_from_fork+0x10/0x18 Fix this by adding respective barrier calls which ensure that all accesses preceding setting of WORK_DONE_BIT are strictly ordered before setting the flag. At the same time add a read barrier after reading of WORK_DONE_BIT in run_ordered_work which ensures all subsequent loads would be strictly ordered after reading the bit. This in turn ensures are all accesses before WORK_DONE_BIT are going to be strictly ordered before any access that can occur in ordered_func.
Severity
6.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 08a9ff3264181986d1d692a4e6fce3669700c9f8 , < bd660a20fea3ec60a49709ef5360f145ec0fe779 (git)
Affected: 08a9ff3264181986d1d692a4e6fce3669700c9f8 , < 637d652d351fd4f263ef302dc52f3971d314e500 (git)
Affected: 08a9ff3264181986d1d692a4e6fce3669700c9f8 , < 804a9d239ae9cbe88e861a7cd62319cc6ec7b136 (git)
Affected: 08a9ff3264181986d1d692a4e6fce3669700c9f8 , < ed058d735a70f4b063323f1a7bb33cda0f987513 (git)
Affected: 08a9ff3264181986d1d692a4e6fce3669700c9f8 , < 670f6b3867c8f0f11e5097f353b164cecfec6179 (git)
Affected: 08a9ff3264181986d1d692a4e6fce3669700c9f8 , < 6adbc07ebcaf8bead08b21687d49e0fc94400987 (git)
Affected: 08a9ff3264181986d1d692a4e6fce3669700c9f8 , < 47e6f9f69153247109042010f3a77579e9dc61ff (git)
Affected: 08a9ff3264181986d1d692a4e6fce3669700c9f8 , < 45da9c1767ac31857df572f0a909fbe88fd5a7e9 (git)
Create a notification for this product.
Linux Linux Affected: 3.15
Unaffected: 0 , < 3.15 (semver)
Unaffected: 4.4.293 , ≤ 4.4.* (semver)
Unaffected: 4.9.291 , ≤ 4.9.* (semver)
Unaffected: 4.14.256 , ≤ 4.14.* (semver)
Unaffected: 4.19.218 , ≤ 4.19.* (semver)
Unaffected: 5.4.162 , ≤ 5.4.* (semver)
Unaffected: 5.10.82 , ≤ 5.10.* (semver)
Unaffected: 5.15.5 , ≤ 5.15.* (semver)
Unaffected: 5.16 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Show details on NVD website
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The call trace was similar to:\\n\\n    pc : submit_compressed_extents+0x38/0x3d0\\n    lr : async_cow_submit+0x50/0xd0\\n    sp : ffff800015d4bc20\\n\\n    \u003cregisters omitted for brevity\u003e\\n\\n    Call trace:\\n     submit_compressed_extents+0x38/0x3d0\\n     async_cow_submit+0x50/0xd0\\n     run_ordered_work+0xc8/0x280\\n     btrfs_work_helper+0x98/0x250\\n     process_one_work+0x1f0/0x4ac\\n     worker_thread+0x188/0x504\\n     kthread+0x110/0x114\\n     ret_from_fork+0x10/0x18\\n\\nFix this by adding respective barrier calls which ensure that all\\naccesses preceding setting of WORK_DONE_BIT are strictly ordered before\\nsetting the flag. At the same time add a read barrier after reading of\\nWORK_DONE_BIT in run_ordered_work which ensures all subsequent loads\\nwould be strictly ordered after reading the bit. This in turn ensures\\nare all accesses before WORK_DONE_BIT are going to be strictly ordered\\nbefore any access that can occur in ordered_func.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: btrfs: arreglo del ordenamiento de memoria entre funciones de trabajo normales y ordenadas No se garantiza que las funciones de trabajo ordenadas sean manejadas por el mismo hilo que ejecut\u00f3 las funciones de trabajo normales. La \u00fanica forma de sincronizar la ejecuci\u00f3n entre funciones normales/ordenadas es a trav\u00e9s de WORK_DONE_BIT, desafortunadamente los bitops utilizados no garantizan ning\u00fan orden. Esto se manifest\u00f3 como fallas aparentemente inexplicables en ARM64, donde async_chunk::inode se ve como no nulo en async_cow_submit, lo que hace que se llame a submission_compressed_extents y se produce una falla porque async_chunk::inode de repente se volvi\u00f3 NULL. El seguimiento de llamadas fue similar a: pc : submission_compressed_extents+0x38/0x3d0 lr : async_cow_submit+0x50/0xd0 sp : ffff800015d4bc20  Seguimiento de llamadas: submission_compressed_extents+0x38/0x3d0 async_cow_submit+0x50/0xd0 run_ordered_work+0xc8/0x280 btrfs_work_helper+0x98/0x250 process_one_work+0x1f0/0x4ac worker_thread+0x188/0x504 kthread+0x110/0x114 ret_from_fork+0x10/0x18 Solucione esto agregando las llamadas de barrera respectivas que garantizan que todos los accesos anteriores a la configuraci\u00f3n de Los bits WORK_DONE_BIT se ordenan estrictamente antes de establecer la bandera. Al mismo tiempo, agregue una barrera de lectura despu\u00e9s de la lectura de WORK_DONE_BIT en run_ordered_work que garantiza que todas las cargas posteriores se ordenar\u00e1n estrictamente despu\u00e9s de leer el bit. Esto, a su vez, garantiza que todos los accesos antes de WORK_DONE_BIT se ordenar\u00e1n estrictamente antes de cualquier acceso que pueda ocurrir en ordered_func.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/btrfs/async-thread.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"08a9ff3264181986d1d692a4e6fce3669700c9f8\",\"lessThan\":\"bd660a20fea3ec60a49709ef5360f145ec0fe779\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"08a9ff3264181986d1d692a4e6fce3669700c9f8\",\"lessThan\":\"637d652d351fd4f263ef302dc52f3971d314e500\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"08a9ff3264181986d1d692a4e6fce3669700c9f8\",\"lessThan\":\"804a9d239ae9cbe88e861a7cd62319cc6ec7b136\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"08a9ff3264181986d1d692a4e6fce3669700c9f8\",\"lessThan\":\"ed058d735a70f4b063323f1a7bb33cda0f987513\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"08a9ff3264181986d1d692a4e6fce3669700c9f8\",\"lessThan\":\"670f6b3867c8f0f11e5097f353b164cecfec6179\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"08a9ff3264181986d1d692a4e6fce3669700c9f8\",\"lessThan\":\"6adbc07ebcaf8bead08b21687d49e0fc94400987\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"08a9ff3264181986d1d692a4e6fce3669700c9f8\",\"lessThan\":\"47e6f9f69153247109042010f3a77579e9dc61ff\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"08a9ff3264181986d1d692a4e6fce3669700c9f8\",\"lessThan\":\"45da9c1767ac31857df572f0a909fbe88fd5a7e9\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/btrfs/async-thread.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"3.15\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"3.15\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"4.4.293\",\"lessThanOrEqual\":\"4.4.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"4.9.291\",\"lessThanOrEqual\":\"4.9.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"4.14.256\",\"lessThanOrEqual\":\"4.14.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"4.19.218\",\"lessThanOrEqual\":\"4.19.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.4.162\",\"lessThanOrEqual\":\"5.4.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.82\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.5\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.16\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L\",\"baseScore\":6.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":2.8,\"impactScore\":3.4}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2024-04-10T19:44:25.164224Z\",\"id\":\"CVE-2021-47189\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2025-11-21T14:36:15+00:00",
      "cve": "CVE-2021-47189",
      "id": "CVE-2021-47189",
      "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: btrfs: fix memory ordering between normal and ordered work functions",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47189.json",
      "version": "3"
    },
    "vulnrichment": {
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guaranteed to be handled by the same thread\\nwhich executed the normal work functions. The only way execution between\\nnormal/ordered functions is synchronized is via the WORK_DONE_BIT,\\nunfortunately the used bitops don\u0027t guarantee any ordering whatsoever.\\n\\nThis manifested as seemingly inexplicable crashes on ARM64, where\\nasync_chunk::inode is seen as non-null in async_cow_submit which causes\\nsubmit_compressed_extents to be called and crash occurs because\\nasync_chunk::inode suddenly became NULL. The call trace was similar to:\\n\\n    pc : submit_compressed_extents+0x38/0x3d0\\n    lr : async_cow_submit+0x50/0xd0\\n    sp : ffff800015d4bc20\\n\\n    \u003cregisters omitted for brevity\u003e\\n\\n    Call trace:\\n     submit_compressed_extents+0x38/0x3d0\\n     async_cow_submit+0x50/0xd0\\n     run_ordered_work+0xc8/0x280\\n     btrfs_work_helper+0x98/0x250\\n     process_one_work+0x1f0/0x4ac\\n     worker_thread+0x188/0x504\\n     kthread+0x110/0x114\\n     ret_from_fork+0x10/0x18\\n\\nFix this by adding respective barrier calls which ensure that all\\naccesses preceding setting of WORK_DONE_BIT are strictly ordered before\\nsetting the flag. At the same time add a read barrier after reading of\\nWORK_DONE_BIT in run_ordered_work which ensures all subsequent loads\\nwould be strictly ordered after reading the bit. This in turn ensures\\nare all accesses before WORK_DONE_BIT are going to be strictly ordered\\nbefore any access that can occur in ordered_func.\"}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2024-11-04T12:01:11.187Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47189\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2024-11-04T12:01:11.187Z\", \"dateReserved\": \"2024-03-25T09:12:14.113Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-04-10T18:56:28.194Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}



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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.