CVE-2021-47282 (GCVE-0-2021-47282)

Vulnerability from cvelistv5 – Published: 2024-05-21 14:20 – Updated: 2026-08-05 08:47
VLAI
Title
spi: bcm2835: Fix out-of-bounds access with more than 4 slaves
Summary
In the Linux kernel, the following vulnerability has been resolved: spi: bcm2835: Fix out-of-bounds access with more than 4 slaves Commit 571e31fa60b3 ("spi: bcm2835: Cache CS register value for ->prepare_message()") limited the number of slaves to 3 at compile-time. The limitation was necessitated by a statically-sized array prepare_cs[] in the driver private data which contains a per-slave register value. The commit sought to enforce the limitation at run-time by setting the controller's num_chipselect to 3: Slaves with a higher chipselect are rejected by spi_add_device(). However the commit neglected that num_chipselect only limits the number of *native* chipselects. If GPIO chipselects are specified in the device tree for more than 3 slaves, num_chipselect is silently raised by of_spi_get_gpio_numbers() and the result are out-of-bounds accesses to the statically-sized array prepare_cs[]. As a bandaid fix which is backportable to stable, raise the number of allowed slaves to 24 (which "ought to be enough for anybody"), enforce the limitation on slave ->setup and revert num_chipselect to 3 (which is the number of native chipselects supported by the controller). An upcoming for-next commit will allow an arbitrary number of slaves.
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 2024-05-23 17:10 UTC
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 571e31fa60b3697d5db26140e16d5c45c51c9815 , < b5502580cf958b094f3b69dfe4eece90eae01fbc (git)
Affected: 571e31fa60b3697d5db26140e16d5c45c51c9815 , < 82a8ffba54d31e97582051cb56ba1f988018681e (git)
Affected: 571e31fa60b3697d5db26140e16d5c45c51c9815 , < 01415ff85a24308059e06ca3e97fd7bf75648690 (git)
Affected: 571e31fa60b3697d5db26140e16d5c45c51c9815 , < 13817d466eb8713a1ffd254f537402f091d48444 (git)
Create a notification for this product.
Linux Linux Affected: 5.4
Unaffected: 0 , < 5.4 (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)
Create a notification for this product.
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                "lang": "en",
                "value": "CWE-787"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
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      "current_release_date": "2026-09-28T00:04:35+00:00",
      "cve": "CVE-2021-47282",
      "id": "CVE-2021-47282",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: spi: bcm2835: Fix out-of-bounds access with more than 4 slaves",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47282.json",
      "version": "3"
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              "dateUpdated": "2024-08-04T05:32:08.008Z",
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            ],
            "title": "CVE Program Container"
          },
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2021-47282",
                    "options": [
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                      },
                      {
                        "Automatable": "no"
                      },
                      {
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                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2024-05-23T17:10:17.644618Z",
                    "version": "2.0.3"
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                  "type": "ssvc"
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              "dateUpdated": "2024-05-23T17:10:22.583Z",
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              "shortName": "CISA-ADP"
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            "title": "CISA ADP Vulnrichment"
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              "programFiles": [
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              "versions": [
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                  "version": "0",
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                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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                  "value": "AV:L - The bcm2835 SPI host driver is reached through local device registration and SPI transfers (e.g. spidev or bound slave drivers) after the controller is instantiated from the platform/device tree; it is not reachable via network protocols or by merely attaching a hot-plugged peripheral.\nAC:L - Once more than four GPIO chipselects are present in the device tree, of_spi_get_gpio_numbers() raises num_chipselect and spi_add_device() accepts high CS indices, so bcm2835_spi_setup()/prepare_message()/DMA paths reliably perform the out-of-bounds accesses with no race or other attacker-uncontrollable condition.\nPR:L - On affected Raspberry Pi and industrial bcm2835 systems, unprivileged local users can open SPI device nodes and trigger transfers that exercise the OOB paths; DT configuration establishing the vulnerable CS count is a realistic deployment precondition rather than a requirement for high privileges at exploit time.\nUI:N - No separate victim action is required; registration at probe and subsequent SPI I/O invoke the vulnerable code without interactive user cooperation.\nS:U - The corruption is confined to kernel memory in the same SPI controller privilege domain and does not cross a VM, IOMMU, or other security authority boundary.\nC:H - Out-of-bounds reads of prepare_cs[] and adjacent bcm2835_spi fields, plus heap corruption from clear_rx_cs[] writes past the allocation, are memory-corruption primitives that can be leveraged for information disclosure.\nI:H - Out-of-bounds writes into prepare_cs[] (overwriting later struct fields such as pointers) and past clear_rx_cs[] into the heap, together with submission of invalid clear_rx_desc[] DMA descriptors, enable integrity compromise and control-flow/DMA abuse.\nA:H - Invalid pointer and DMA descriptor use from the corrupted bcm2835_spi state can cause kernel oops/panic or hangs, yielding a full availability impact."
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        "assignerShortName": "Linux",
        "cveId": "CVE-2021-47282",
        "datePublished": "2024-05-21T14:20:08.155Z",
        "dateReserved": "2024-05-21T13:27:52.128Z",
        "dateUpdated": "2026-08-05T08:47:04.965Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
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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.

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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.
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  • 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.



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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.