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FKIE_CVE-2026-89704

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-09-14 13:19
Severity
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: sample writeback error cursor before async COPY loop _nfsd_copy_file_range() samples dst->f_wb_err into "since" after the copy loop, then uses it to detect writeback errors via filemap_check_wb_err() once vfs_fsync_range() returns. Because the nfsd_file cache reuses a single struct file across requests targeting the same inode, a concurrent COMMIT or stable WRITE on dst advances dst->f_wb_err to the current mapping->wb_err via file_check_and_advance_wb_err() during its own vfs_fsync_range(). If that advancement lands between the writeback error appearing in mapping->wb_err and the COPY worker sampling "since", the worker captures the already-advanced cursor, errseq_check() sees cur == since and returns zero, and NFSD4_COPY_F_COMMITTED is set even though writeback failed. CB_OFFLOAD then encodes wr_stable_how = FILE_SYNC4, the client treats the copied data as durable, and the failure becomes silent data loss. Sample since once at the start of the function. The cursor then reflects state in effect before this COPY issues any writes, and filemap_check_wb_err() detects any error that occurs during the copy regardless of which thread first observes it. This matches the pattern used by nfsd_vfs_write() and nfsd4_clone_file_range().
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/20a67a7d18221af736f124770c2c5e859b479046
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/322422d66d1a04434a0dcc0c9d3a4c4b3f225117
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/435e4246c7dfff2fbd76dfdbf91975d5d9f788c9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4728504c021656128a07f4693af80ed4a5fcc863
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/52b2db7a72e19ac2686fa4b2a52406661e7bf9e2
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8277d4a11ae2cb5495842be558fd946032c24363
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9f539a1c0791f907eb4e6d04b43178d9962e2def
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a1cbafe756cd5e6ab0e099062f37da7a5b081169
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "435e4246c7dfff2fbd76dfdbf91975d5d9f788c9",
              "status": "affected",
              "version": "f14816f2f928c560d28ba344af689f56efcd6f55",
              "versionType": "git"
            },
            {
              "lessThan": "9f539a1c0791f907eb4e6d04b43178d9962e2def",
              "status": "affected",
              "version": "3145fe0ebb16e1715ad541a301bc6675c8375fcd",
              "versionType": "git"
            },
            {
              "lessThan": "4728504c021656128a07f4693af80ed4a5fcc863",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "322422d66d1a04434a0dcc0c9d3a4c4b3f225117",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "52b2db7a72e19ac2686fa4b2a52406661e7bf9e2",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "8277d4a11ae2cb5495842be558fd946032c24363",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "a1cbafe756cd5e6ab0e099062f37da7a5b081169",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "20a67a7d18221af736f124770c2c5e859b479046",
              "status": "affected",
              "version": "555dbf1a9aac6d3150c8b52fa35f768a692f4eeb",
              "versionType": "git"
            },
            {
              "lessThan": "5.10.270",
              "status": "affected",
              "version": "5.10.124",
              "versionType": "semver"
            },
            {
              "lessThan": "5.15.221",
              "status": "affected",
              "version": "5.15.49",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.17"
            },
            {
              "lessThan": "5.17",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.270",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "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\nnfsd: sample writeback error cursor before async COPY loop\n\n_nfsd_copy_file_range() samples dst-\u003ef_wb_err into \"since\"\nafter the copy loop, then uses it to detect writeback errors\nvia filemap_check_wb_err() once vfs_fsync_range() returns.\nBecause the nfsd_file cache reuses a single struct file\nacross requests targeting the same inode, a concurrent\nCOMMIT or stable WRITE on dst advances dst-\u003ef_wb_err to the\ncurrent mapping-\u003ewb_err via file_check_and_advance_wb_err()\nduring its own vfs_fsync_range(). If that advancement lands\nbetween the writeback error appearing in mapping-\u003ewb_err\nand the COPY worker sampling \"since\", the worker captures\nthe already-advanced cursor, errseq_check() sees cur ==\nsince and returns zero, and NFSD4_COPY_F_COMMITTED is set\neven though writeback failed. CB_OFFLOAD then encodes\nwr_stable_how = FILE_SYNC4, the client treats the copied\ndata as durable, and the failure becomes silent data loss.\n\nSample since once at the start of the function. The cursor\nthen reflects state in effect before this COPY issues any\nwrites, and filemap_check_wb_err() detects any error that\noccurs during the copy regardless of which thread first\nobserves it. This matches the pattern used by\nnfsd_vfs_write() and nfsd4_clone_file_range()."
    }
  ],
  "id": "CVE-2026-89704",
  "lastModified": "2026-09-14T13:19:20.367",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-11T20:19:57.657",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/20a67a7d18221af736f124770c2c5e859b479046"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/322422d66d1a04434a0dcc0c9d3a4c4b3f225117"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/435e4246c7dfff2fbd76dfdbf91975d5d9f788c9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4728504c021656128a07f4693af80ed4a5fcc863"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/52b2db7a72e19ac2686fa4b2a52406661e7bf9e2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8277d4a11ae2cb5495842be558fd946032c24363"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9f539a1c0791f907eb4e6d04b43178d9962e2def"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a1cbafe756cd5e6ab0e099062f37da7a5b081169"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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