tty: serial: sh-sci: fix RSCI FIFO overrun handling

{
  "id": "5447f35df057201937921d53c7aa5be9f608562d1fdb23f67770823ce6354bf9",
  "url": "https://osv.dev/vulnerability/CVE-2025-40222",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "tty: serial: sh-sci: fix RSCI FIFO overrun handling",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: tty: serial: sh-sci: fix RSCI FIFO overrun handling The receive error handling code is shared between RSCI and all other SCIF port types, but the RSCI overrun_reg is specified as a memory offset, while for other SCIF types it is an enum value used to index into the sci_port_params->regs array, as mentioned above the sci_serial_in() function. For RSCI, the overrun_reg is CSR (0x48), causing the sci_getreg() call inside the sci_handle_fifo_overrun() function to index outside the bounds of the regs array, which currently has a size of 20, as specified by SCI_NR_REGS. Because of this, we end up accessing memory outside of RSCI's rsci_port_params structure, which, when interpreted as a plat_sci_reg, happens to have a non-zero size, causing the following WARN when sci_serial_in() is called, as the accidental size does not match the supported register sizes. The existence of the overrun_reg needs to be checked because SCIx_SH3_SCIF_REGTYPE has overrun_reg set to SCLSR, but SCLSR is not present in the regs array. Avoid calling sci_getreg() for port types which don't use standard register handling. Use the ops->read_reg() and ops->write_reg() functions to properly read and write registers for RSCI, and change the type of the status variable to accommodate the 32-bit CSR register. sci_getreg() and sci_serial_in() are also called with overrun_reg in the sci_mpxed_interrupt() interrupt handler, but that code path is not ",
    "evidence": "osv:CVE-2025-40222",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.17.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2025-40222",
      "aliases": [
        "CVE-2025-40222"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0666e3fe95ab55c295984f2f51277ec27d3f190c"
                },
                {
                  "fixed": "2ec9bbd09a6cdf5b8c726be34f29630faf585d07"
                },
                {
                  "fixed": "ef8fef45c74b5a0059488fda2df65fa133f7d7d0"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-40222.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.17.0"
                },
                {
                  "fixed": "6.17.6"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-40222.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:53.232126068Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/2ec9bbd09a6cdf5b8c726be34f29630faf585d07",
        "https://git.kernel.org/stable/c/ef8fef45c74b5a0059488fda2df65fa133f7d7d0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/40xxx/CVE-2025-40222.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-40222",
        "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/2025/40xxx/CVE-2025-40222.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-40222",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 522291,
  "published_at": "2025-12-04T15:31:14.142+00:00"
}