iio: adc: ad_sigma_delta: fix clear_pending_event for registerless devices

{
  "id": "6db43c94ea8fa846f125277ca2a54ea7589844a21a0abf4a4efbf03d0f8a46f4",
  "url": "https://osv.dev/vulnerability/CVE-2026-64502",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "iio: adc: ad_sigma_delta: fix clear_pending_event for registerless devices",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: iio: adc: ad_sigma_delta: fix clear_pending_event for registerless devices ad_sigma_delta_clear_pending_event() falls through to the status register read path for devices with has_registers = false and no rdy_gpiod. For such devices, ad_sd_read_reg() skips the address byte entirely and clocks raw MISO bytes with no address phase — making it byte-for-byte identical to reading conversion data. If a pending conversion result is present, this partially consumes it and corrupts the data stream for the subsequent ad_sd_read_reg() call in ad_sigma_delta_single_conversion(). Furthermore, with num_resetclks = 0 on these devices, data_read_len evaluates to 0. If the clocked byte has bit 7 clear, pending_event is set and the code attempts memset(data + 2, 0xff, 0 - 1), overflowing to SIZE_MAX and corrupting the heap. Fix by returning 0 immediately when neither rdy_gpiod nor has_registers is set. This is safe for all current registerless devices: ad7191 and ad7780 (with powerdown GPIO) are reset between conversions by CS deassertion, so there is no stale result to drain; ad7780 (without powerdown GPIO) and max11205 are continuously-converting and cycle ~DRDY at the output data rate regardless of whether the previous result was read, so the next falling edge fires naturally. A future registerless device that holds ~DRDY asserted until data is read would be broken by this early return and would require either num_resetclks",
    "evidence": "osv:CVE-2026-64502",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.39",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-64502",
      "aliases": [
        "CVE-2026-64502"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "132d44dc6966c1cf841ffe0f6f048165687e870b"
                },
                {
                  "fixed": "3394e0b3328422431cadaf314fa58d3717ed4936"
                },
                {
                  "fixed": "3bceb26dfaf7ba805b459e41c1d0ba916862dade"
                },
                {
                  "fixed": "91bc6767a4f55dc470d8a56b55b9f2ea09094efe"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64502.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.14.0"
                },
                {
                  "fixed": "6.18.39"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64502.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:38.757478954Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/3394e0b3328422431cadaf314fa58d3717ed4936",
        "https://git.kernel.org/stable/c/3bceb26dfaf7ba805b459e41c1d0ba916862dade",
        "https://git.kernel.org/stable/c/91bc6767a4f55dc470d8a56b55b9f2ea09094efe",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64502.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64502",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64502.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-64502",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 506318,
  "published_at": "2026-07-25T08:51:57.477+00:00"
}