CVE-2026-80876 (GCVE-0-2026-80876)

Vulnerability from cvelistv5 – Published: 2026-09-04 16:48 – Updated: 2026-09-04 16:48
VLAI
Title
ring-buffer: Fix event length with forced 8-byte alignment
Summary
In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Fix event length with forced 8-byte alignment When RB_FORCE_8BYTE_ALIGNMENT is true, rb_calculate_event_length() reserves the space of event->array[0] for placing the data length and rb_update_event() stores the data length in event->array[0] accordingly. As a result the whole event length will add extra 4 bytes for sizeof(event.array[0]) unconditionally. But ring_buffer_event_length() only subtracts the sizeof(event->array[0]) for events larger than RB_MAX_SMALL_DATA + sizeof(event->array[0]). As a result, small events on architectures with RB_FORCE_8BYTE_ALIGNMENT=true report a data length that is 4 bytes larger than expected. To fix it, add the RB_FORCE_8BYTE_ALIGNMENT as a condition to subtract the size of that length field whenever RB_FORCE_8BYTE_ALIGNMENT is true. This issue is observed in a riscv64 kernel with CONFIG_HAVE_64BIT_ALIGNED_ACCESS set to y, when we run ftrace selftest trace_marker_raw.tc, we get the weird log: for cases where the id is 1..100, the number of data field is 8*N, but once id exceeds 100, the number of data field becomes 8*N+4: # 1 buf: 58 00 00 00 80 5e d1 63 (number of data field is 8*1) ... # a buf: 58 ... (number of data field is 8*2) ... # 64 buf: 58 ... (number of data field is 8*13) # 65 buf: 58 ... (number of data field is 8*13+4) After applying this change, the number of data field keeps being 8*N+4 consistently.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 2271048d1b3b0aabf83d25b29c20646dcabedc05 , < 7c9f0ccf9f04142458d2ac3d39414f4acae242f0 (git)
Affected: 2271048d1b3b0aabf83d25b29c20646dcabedc05 , < 24c3fa71f9947b0e1f3b954db1b769b44140192e (git)
Affected: 2271048d1b3b0aabf83d25b29c20646dcabedc05 , < 14057268e79654c3e8ea2c9b5204cb9644b2964d (git)
Affected: 2271048d1b3b0aabf83d25b29c20646dcabedc05 , < dbcb8635b1eb7603818591cf745c7b1d714f7ac6 (git)
Affected: 2271048d1b3b0aabf83d25b29c20646dcabedc05 , < cfada73fabe2ccc06ec77fe2ceaa088689213326 (git)
Affected: 2271048d1b3b0aabf83d25b29c20646dcabedc05 , < ec5e96aee75d27779b9a860307679f13f33adb0c (git)
Affected: 2271048d1b3b0aabf83d25b29c20646dcabedc05 , < 3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992 (git)
Affected: 2271048d1b3b0aabf83d25b29c20646dcabedc05 , < c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0 (git)
Create a notification for this product.
Linux Linux Affected: 2.6.34
Unaffected: 0 , < 2.6.34 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 5.15.212 , ≤ 5.15.* (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Show details on NVD website
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Fix event length with forced 8-byte alignment\n\nWhen RB_FORCE_8BYTE_ALIGNMENT is true, rb_calculate_event_length()\nreserves the space of event-\u003earray[0] for placing the data length and\nrb_update_event() stores the data length in event-\u003earray[0]\naccordingly. As a result the whole event length will add extra 4 bytes\nfor sizeof(event.array[0]) unconditionally.\n\nBut ring_buffer_event_length() only subtracts the\nsizeof(event-\u003earray[0]) for events larger than RB_MAX_SMALL_DATA +\nsizeof(event-\u003earray[0]). As a result, small events on architectures\nwith RB_FORCE_8BYTE_ALIGNMENT=true report a data length that is 4\nbytes larger than expected.\n\nTo fix it, add the RB_FORCE_8BYTE_ALIGNMENT as a condition to subtract\nthe size of that length field whenever RB_FORCE_8BYTE_ALIGNMENT is\ntrue.\n\nThis issue is observed in a riscv64 kernel with\nCONFIG_HAVE_64BIT_ALIGNED_ACCESS set to y, when we run ftrace selftest\ntrace_marker_raw.tc, we get the weird log: for cases where the id is\n1..100, the number of data field is 8*N, but once id exceeds 100, the\nnumber of data field becomes 8*N+4:\n # 1 buf: 58 00 00 00 80 5e d1 63 (number of data field is 8*1)\n ...\n # a buf: 58 ...                  (number of data field is 8*2)\n ...\n # 64 buf: 58 ...                 (number of data field is 8*13)\n # 65 buf: 58 ...                 (number of data field is 8*13+4)\n\nAfter applying this change, the number of data field keeps being 8*N+4\nconsistently."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-04T16:48:50.082Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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        },
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          "url": "https://git.kernel.org/stable/c/24c3fa71f9947b0e1f3b954db1b769b44140192e"
        },
        {
          "url": "https://git.kernel.org/stable/c/14057268e79654c3e8ea2c9b5204cb9644b2964d"
        },
        {
          "url": "https://git.kernel.org/stable/c/dbcb8635b1eb7603818591cf745c7b1d714f7ac6"
        },
        {
          "url": "https://git.kernel.org/stable/c/cfada73fabe2ccc06ec77fe2ceaa088689213326"
        },
        {
          "url": "https://git.kernel.org/stable/c/ec5e96aee75d27779b9a860307679f13f33adb0c"
        },
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          "url": "https://git.kernel.org/stable/c/3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992"
        },
        {
          "url": "https://git.kernel.org/stable/c/c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0"
        }
      ],
      "title": "ring-buffer: Fix event length with forced 8-byte alignment",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80876",
    "datePublished": "2026-09-04T16:48:50.082Z",
    "dateReserved": "2026-08-26T14:34:25.799Z",
    "dateUpdated": "2026-09-04T16:48:50.082Z",
    "state": "PUBLISHED"
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      "date": "2026-10-03",
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Fix event length with forced 8-byte alignment\n\nWhen RB_FORCE_8BYTE_ALIGNMENT is true, rb_calculate_event_length()\nreserves the space of event-\u003earray[0] for placing the data length and\nrb_update_event() stores the data length in event-\u003earray[0]\naccordingly. As a result the whole event length will add extra 4 bytes\nfor sizeof(event.array[0]) unconditionally.\n\nBut ring_buffer_event_length() only subtracts the\nsizeof(event-\u003earray[0]) for events larger than RB_MAX_SMALL_DATA +\nsizeof(event-\u003earray[0]). As a result, small events on architectures\nwith RB_FORCE_8BYTE_ALIGNMENT=true report a data length that is 4\nbytes larger than expected.\n\nTo fix it, add the RB_FORCE_8BYTE_ALIGNMENT as a condition to subtract\nthe size of that length field whenever RB_FORCE_8BYTE_ALIGNMENT is\ntrue.\n\nThis issue is observed in a riscv64 kernel with\nCONFIG_HAVE_64BIT_ALIGNED_ACCESS set to y, when we run ftrace selftest\ntrace_marker_raw.tc, we get the weird log: for cases where the id is\n1..100, the number of data field is 8*N, but once id exceeds 100, the\nnumber of data field becomes 8*N+4:\n # 1 buf: 58 00 00 00 80 5e d1 63 (number of data field is 8*1)\n ...\n # a buf: 58 ...                  (number of data field is 8*2)\n ...\n # 64 buf: 58 ...                 (number of data field is 8*13)\n # 65 buf: 58 ...                 (number of data field is 8*13+4)\n\nAfter applying this change, the number of data field keeps being 8*N+4\nconsistently."
          }
        ],
        "id": "CVE-2026-80876",
        "lastModified": "2026-09-04T17:16:59.640",
        "metrics": {},
        "published": "2026-09-04T17:16:59.640",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/7c9f0ccf9f04142458d2ac3d39414f4acae242f0"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/cfada73fabe2ccc06ec77fe2ceaa088689213326"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/dbcb8635b1eb7603818591cf745c7b1d714f7ac6"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/ec5e96aee75d27779b9a860307679f13f33adb0c"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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