mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()

{
  "id": "2cb05ef1713a488d830ff936ac79a4251c1fce10e623f6b77b1751e0f1467103",
  "url": "https://osv.dev/vulnerability/CVE-2026-93048",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition() mtd_add_partition() does not reject the special offset value MTDPART_OFS_RETAIN (-3), which leads to a WARN_ON in add_mtd_device() when called through the BLKPG ioctl on NAND devices. The RETAIN value depends on cur_offset being the end of the previous partition, but in the dynamic partition path cur_offset equals the offset argument itself, causing undefined behavior. Commit 5daa7b21496a (\"mtd: prepare partition add and del functions for ioctl requests\") introduced mtd_add_partition() and correctly rejected MTDPART_OFS_APPEND (-1) and MTDPART_OFS_NXTBLK (-2), since those special offsets rely on cur_offset tracking the previous partition's end. However, commit 1a31368bf92e (\"mtd: add a flags for partitions which should just leave smth. after them\") later added MTDPART_OFS_RETAIN (-3) for the static partition table path without updating mtd_add_partition() to also reject this value. With offset=-3 passed via BLKPG, the RETAIN size calculation in allocate_partition() underflows (parent_size - 0xFFFFFFFFFFFFFFFD = parent_size + 3). If the underflow result does not appear to leave enough space, allocate_partition() jumps to out_register via goto, skipping erasesize initialization. This results in erasesize=0, which triggers: WARN_ON((!mtd->erasesize || !master->_erase) && !(mtd->flags & MTD_NO_ERASE)) in add_mtd_device(). If the underflow result appears ",
    "evidence": "osv:CVE-2026-93048",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.270",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.221",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.188",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.157",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.110",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.52",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-93048",
      "aliases": [
        "CVE-2026-93048"
      ],
      "affected": [
        {
          "ranges": [
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
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                  "fixed": "701c3ae7273e1adc20db5d97c42e0139b479f16b"
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                {
                  "fixed": "6aaab2ace3f7b55733d904e5549acf8405f03642"
                },
                {
                  "fixed": "181c1bff940e7d3e34ca485d37e3cdbfe409203c"
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                  "fixed": "a536eb57be58442b19398b2783071007ecfb1735"
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                  "fixed": "e204e5c49a012f99638633fdbd773e3c86260053"
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                  "fixed": "398aca2f90122d5abbabff1079deaeb885fe9e40"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93048.json"
          }
        },
        {
          "ranges": [
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              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "3.2.0"
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                {
                  "fixed": "5.10.270"
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              "type": "ECOSYSTEM",
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                {
                  "introduced": "5.11.0"
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93048.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:53.023383870Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/181c1bff940e7d3e34ca485d37e3cdbfe409203c",
        "https://git.kernel.org/stable/c/398aca2f90122d5abbabff1079deaeb885fe9e40",
        "https://git.kernel.org/stable/c/6aaab2ace3f7b55733d904e5549acf8405f03642",
        "https://git.kernel.org/stable/c/701c3ae7273e1adc20db5d97c42e0139b479f16b",
        "https://git.kernel.org/stable/c/a536eb57be58442b19398b2783071007ecfb1735",
        "https://git.kernel.org/stable/c/b759d5bb6265419344ee9729fd0dc07ad85719d8",
        "https://git.kernel.org/stable/c/c645f6dd1af2ecc70fd3578e141f2f71fa9e4eff",
        "https://git.kernel.org/stable/c/e204e5c49a012f99638633fdbd773e3c86260053",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93048.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-93048",
        "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/2026/93xxx/CVE-2026-93048.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-93048",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 521918,
  "published_at": "2026-09-17T16:10:39.008+00:00"
}