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CVE-2021-47261 (GCVE-0-2021-47261)

Vulnerability from cvelistv5 – Published: 2024-05-21 14:19 – Updated: 2026-08-05 08:47
VLAI
Title
IB/mlx5: Fix initializing CQ fragments buffer
Summary
In the Linux kernel, the following vulnerability has been resolved: IB/mlx5: Fix initializing CQ fragments buffer The function init_cq_frag_buf() can be called to initialize the current CQ fragments buffer cq->buf, or the temporary cq->resize_buf that is filled during CQ resize operation. However, the offending commit started to use function get_cqe() for getting the CQEs, the issue with this change is that get_cqe() always returns CQEs from cq->buf, which leads us to initialize the wrong buffer, and in case of enlarging the CQ we try to access elements beyond the size of the current cq->buf and eventually hit a kernel panic. [exception RIP: init_cq_frag_buf+103] [ffff9f799ddcbcd8] mlx5_ib_resize_cq at ffffffffc0835d60 [mlx5_ib] [ffff9f799ddcbdb0] ib_resize_cq at ffffffffc05270df [ib_core] [ffff9f799ddcbdc0] llt_rdma_setup_qp at ffffffffc0a6a712 [llt] [ffff9f799ddcbe10] llt_rdma_cc_event_action at ffffffffc0a6b411 [llt] [ffff9f799ddcbe98] llt_rdma_client_conn_thread at ffffffffc0a6bb75 [llt] [ffff9f799ddcbec8] kthread at ffffffffa66c5da1 [ffff9f799ddcbf50] ret_from_fork_nospec_begin at ffffffffa6d95ddd Fix it by getting the needed CQE by calling mlx5_frag_buf_get_wqe() that takes the correct source buffer as a parameter.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-05-21 18:50 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 388ca8be00370db132464e27f745b8a0add19fcb , < 1ec2dcd680c71d0d36fa25638b327a468babd5c9 (git)
Affected: 388ca8be00370db132464e27f745b8a0add19fcb , < e3ecd9c09fcc10cf6b2bc67e2990c397c40a8c26 (git)
Affected: 388ca8be00370db132464e27f745b8a0add19fcb , < 91f7fdc4cc10542ca1045c06aad23365f0d067e0 (git)
Affected: 388ca8be00370db132464e27f745b8a0add19fcb , < 3e670c54eda238cb8a1ea93538a79ae89285c1c4 (git)
Affected: 388ca8be00370db132464e27f745b8a0add19fcb , < 2ba0aa2feebda680ecfc3c552e867cf4d1b05a3a (git)
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Linux Linux Affected: 4.17
Unaffected: 0 , < 4.17 (semver)
Unaffected: 4.19.195 , ≤ 4.19.* (semver)
Unaffected: 5.4.126 , ≤ 5.4.* (semver)
Unaffected: 5.10.44 , ≤ 5.10.* (semver)
Unaffected: 5.12.11 , ≤ 5.12.* (semver)
Unaffected: 5.13 , ≤ * (original_commit_for_fix)
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Se puede llamar a la funci\u00f3n init_cq_frag_buf() para inicializar el b\u00fafer de fragmentos CQ actual cq-\u0026gt;buf, o el cq-\u0026gt;resize_buf temporal que es rellenado durante la operaci\u00f3n de cambio de tama\u00f1o de CQ. Sin embargo, la confirmaci\u00f3n infractora comenz\u00f3 a usar la funci\u00f3n get_cqe() para obtener los CQE, el problema con este cambio es que get_cqe() siempre devuelve CQE desde cq-\u0026gt;buf, lo que nos lleva a inicializar el b\u00fafer incorrecto y, en caso de ampliarlo, En el CQ intentamos acceder a elementos m\u00e1s all\u00e1 del tama\u00f1o del cq-\u0026gt;buf actual y finalmente entramos en p\u00e1nico en el kernel. [excepci\u00f3n RIP: init_cq_frag_buf+103] [ffff9f799ddcbcd8] mlx5_ib_resize_cq en fffffffc0835d60 [mlx5_ib] [ffff9f799ddcbdb0] ib_resize_cq en fffffffc05270df [ib_core] [ffff9f799ddcbdc0] _rdma_setup_qp en ffffffffc0a6a712 [llt] [ffff9f799ddcbe10] llt_rdma_cc_event_action en ffffffffc0a6b411 [llt] [ffff9f799ddcbe98] llt_rdma_client_conn_thread en ffffffffc0a6bb75 [llt] [ffff9f799ddcbec8] kthread en ffffffffa66c5da1 [ffff9f799ddcbf50] ret_from_fork_nospec_begin en ffffffffa6d95ddd Arr\u00e9glelo obteniendo el CQE necesario llamando a mlx5_frag_buf_get_wqe() que toma el b\u00fafer de origen correcto como 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    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-08-04T23:03:38+00:00",
      "cve": "CVE-2021-47261",
      "id": "CVE-2021-47261",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:known_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: IB/mlx5: Fix initializing CQ fragments buffer",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47261.json",
      "version": "3"
    },
    "vulnrichment": {
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or attacker-uncontrollable condition required.\\nPR:L - In the realistic deployment shown by the crash (RDMA ULP calling ib_resize_cq during client connection setup), unprivileged local workloads can drive that connection path; uverbs devices are also world-accessible (0666), and when uncertain between PR:L and PR:H the higher severity applies.\\nUI:N - No separate victim action is required; the attacker\\u2019s own local activity that causes kernel CQ enlargement triggers the bug.\\nS:U - Impact is kernel memory corruption within the host kernel security authority; this is not a VM escape, IOMMU bypass, or other cross-boundary issue.\\nC:H - Out-of-bounds indexing of cq-\u003ebuf.fbc.frags yields a corrupted pointer write into kernel memory; per guidance, exploitable memory corruption supports high confidentiality impact.\\nI:H - This is an out-of-bounds write through an attacker-influenced frag index into kernel memory, which can be leveraged for integrity compromise and control-flow hijacking.\\nA:H - The commit documents a kernel panic in init_cq_frag_buf when enlarging the CQ, which is high availability impact.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"388ca8be00370db132464e27f745b8a0add19fcb\", \"lessThan\": \"1ec2dcd680c71d0d36fa25638b327a468babd5c9\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"388ca8be00370db132464e27f745b8a0add19fcb\", \"lessThan\": \"e3ecd9c09fcc10cf6b2bc67e2990c397c40a8c26\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"388ca8be00370db132464e27f745b8a0add19fcb\", \"lessThan\": \"91f7fdc4cc10542ca1045c06aad23365f0d067e0\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"388ca8be00370db132464e27f745b8a0add19fcb\", \"lessThan\": \"3e670c54eda238cb8a1ea93538a79ae89285c1c4\", \"versionType\": \"git\"}, 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initialize the current CQ\\nfragments buffer cq-\u003ebuf, or the temporary cq-\u003eresize_buf that is filled\\nduring CQ resize operation.\\n\\nHowever, the offending commit started to use function get_cqe() for\\ngetting the CQEs, the issue with this change is that get_cqe() always\\nreturns CQEs from cq-\u003ebuf, which leads us to initialize the wrong buffer,\\nand in case of enlarging the CQ we try to access elements beyond the size\\nof the current cq-\u003ebuf and eventually hit a kernel panic.\\n\\n [exception RIP: init_cq_frag_buf+103]\\n  [ffff9f799ddcbcd8] mlx5_ib_resize_cq at ffffffffc0835d60 [mlx5_ib]\\n  [ffff9f799ddcbdb0] ib_resize_cq at ffffffffc05270df [ib_core]\\n  [ffff9f799ddcbdc0] llt_rdma_setup_qp at ffffffffc0a6a712 [llt]\\n  [ffff9f799ddcbe10] llt_rdma_cc_event_action at ffffffffc0a6b411 [llt]\\n  [ffff9f799ddcbe98] llt_rdma_client_conn_thread at ffffffffc0a6bb75 [llt]\\n  [ffff9f799ddcbec8] kthread at ffffffffa66c5da1\\n  [ffff9f799ddcbf50] ret_from_fork_nospec_begin at ffffffffa6d95ddd\\n\\nFix it by getting the needed CQE by calling mlx5_frag_buf_get_wqe() that\\ntakes the correct source buffer as a parameter.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.19.195\", \"versionStartIncluding\": \"4.17\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.126\", \"versionStartIncluding\": \"4.17\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.44\", \"versionStartIncluding\": \"4.17\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.12.11\", \"versionStartIncluding\": \"4.17\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, 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      "cveMetadata": "{\"cveId\": \"CVE-2021-47261\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T08:47:01.751Z\", \"dateReserved\": \"2024-05-21T13:27:52.126Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-05-21T14:19:54.025Z\", \"assignerShortName\": \"Linux\"}",
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  }
}



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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.


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