fsdax: dax_unshare_iter needs to copy entire blocks

{
  "id": "816cd6aa2bc6afe6368c358966e95085e4391fcc57593bf44f96a657b5418954",
  "url": "https://osv.dev/vulnerability/CVE-2024-50250",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "fsdax: dax_unshare_iter needs to copy entire blocks",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: fsdax: dax_unshare_iter needs to copy entire blocks The code that copies data from srcmap to iomap in dax_unshare_iter is very very broken, which bfoster's recent fsx changes have exposed. If the pos and len passed to dax_file_unshare are not aligned to an fsblock boundary, the iter pos and length in the _iter function will reflect this unalignment. dax_iomap_direct_access always returns a pointer to the start of the kmapped fsdax page, even if its pos argument is in the middle of that page. This is catastrophic for data integrity when iter->pos is not aligned to a page, because daddr/saddr do not point to the same byte in the file as iter->pos. Hence we corrupt user data by copying it to the wrong place. If iter->pos + iomap_length() in the _iter function not aligned to a page, then we fail to copy a full block, and only partially populate the destination block. This is catastrophic for data confidentiality because we expose stale pmem contents. Fix both of these issues by aligning copy_pos/copy_len to a page boundary (remember, this is fsdax so 1 fsblock == 1 base page) so that we always copy full blocks. We're not done yet -- there's no call to invalidate_inode_pages2_range, so programs that have the file range mmap'd will continue accessing the old memory mapping after the file metadata updates have completed. Be careful with the return value -- if the unshare succeeds, we still need to return the number ",
    "evidence": "osv:CVE-2024-50250",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.116",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.60",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.11.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2024-50250",
      "aliases": [
        "CVE-2024-50250"
      ],
      "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": "1bec6782a25c9b92c203ea7a1b3e3dc6a468cbc4"
                },
                {
                  "fixed": "bdbc96c23197d773a7d1bf03e4f11de593b0ff28"
                }
              ]
            },
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "d984648e428bf88cbd94ebe346c73632cb92fffb"
                },
                {
                  "fixed": "9bc18bb476e50e32e5d08f2734d63d63e0fa528c"
                },
                {
                  "fixed": "8e9c0f500b42216ef930f5c0d1703989a451913d"
                },
                {
                  "fixed": "50793801fc7f6d08def48754fb0f0706b0cfc394"
                }
              ]
            },
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "6.1.113"
                },
                {
                  "fixed": "6.1.116"
                }
              ]
            }
          ],
          "versions": [
            "v6.1.115",
            "v6.1.114",
            "v6.1.113"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-50250.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "6.1.116"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.60"
                },
                {
                  "fixed": "6.11.7"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-50250.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.265650888Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/50793801fc7f6d08def48754fb0f0706b0cfc394",
        "https://git.kernel.org/stable/c/8e9c0f500b42216ef930f5c0d1703989a451913d",
        "https://git.kernel.org/stable/c/9bc18bb476e50e32e5d08f2734d63d63e0fa528c",
        "https://git.kernel.org/stable/c/bdbc96c23197d773a7d1bf03e4f11de593b0ff28",
        "https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/50xxx/CVE-2024-50250.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2024-50250",
        "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/2024/50xxx/CVE-2024-50250.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2024-50250",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496971,
  "published_at": "2024-11-09T10:14:59.003+00:00"
}