FKIE_CVE-2026-80876

Vulnerability from fkie_nvd - Published: 2026-09-04 17:16 - Updated: 2026-09-04 17:16
Severity
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/14057268e79654c3e8ea2c9b5204cb9644b2964d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/24c3fa71f9947b0e1f3b954db1b769b44140192e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7c9f0ccf9f04142458d2ac3d39414f4acae242f0
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cfada73fabe2ccc06ec77fe2ceaa088689213326
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dbcb8635b1eb7603818591cf745c7b1d714f7ac6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ec5e96aee75d27779b9a860307679f13f33adb0c
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/ring_buffer.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "7c9f0ccf9f04142458d2ac3d39414f4acae242f0",
              "status": "affected",
              "version": "2271048d1b3b0aabf83d25b29c20646dcabedc05",
              "versionType": "git"
            },
            {
              "lessThan": "24c3fa71f9947b0e1f3b954db1b769b44140192e",
              "status": "affected",
              "version": "2271048d1b3b0aabf83d25b29c20646dcabedc05",
              "versionType": "git"
            },
            {
              "lessThan": "14057268e79654c3e8ea2c9b5204cb9644b2964d",
              "status": "affected",
              "version": "2271048d1b3b0aabf83d25b29c20646dcabedc05",
              "versionType": "git"
            },
            {
              "lessThan": "dbcb8635b1eb7603818591cf745c7b1d714f7ac6",
              "status": "affected",
              "version": "2271048d1b3b0aabf83d25b29c20646dcabedc05",
              "versionType": "git"
            },
            {
              "lessThan": "cfada73fabe2ccc06ec77fe2ceaa088689213326",
              "status": "affected",
              "version": "2271048d1b3b0aabf83d25b29c20646dcabedc05",
              "versionType": "git"
            },
            {
              "lessThan": "ec5e96aee75d27779b9a860307679f13f33adb0c",
              "status": "affected",
              "version": "2271048d1b3b0aabf83d25b29c20646dcabedc05",
              "versionType": "git"
            },
            {
              "lessThan": "3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992",
              "status": "affected",
              "version": "2271048d1b3b0aabf83d25b29c20646dcabedc05",
              "versionType": "git"
            },
            {
              "lessThan": "c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0",
              "status": "affected",
              "version": "2271048d1b3b0aabf83d25b29c20646dcabedc05",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/ring_buffer.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.34"
            },
            {
              "lessThan": "2.6.34",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.261",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.212",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.178",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.145",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.97",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.40",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "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",
      "url": "https://git.kernel.org/stable/c/14057268e79654c3e8ea2c9b5204cb9644b2964d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/24c3fa71f9947b0e1f3b954db1b769b44140192e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992"
    },
    {
      "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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