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GHSA-F5CM-4MMF-92C9

Vulnerability from github – Published: 2026-06-25 09:31 – Updated: 2026-06-28 09:31

Details

In the Linux kernel, the following vulnerability has been resolved:

iomap: avoid potential null folio->mapping deref during error reporting

When a buffered read fails, iomap_finish_folio_read() reports the error with fserror_report_io(folio->mapping->host, ...). This is called after ifs->read_bytes_pending has been decremented by the bytes attempted to be read.

For a folio split across multiple read completions, the folio is only guaranteed to stay locked while read_bytes_pending > 0. Once iomap_finish_folio_read() decrements read_bytes_pending, another in-flight read can complete and end the read on the folio, which unlocks it. This allows truncate logic to run and detach the folio (set folio->mapping to NULL). The error reporting path then can dereference a NULL folio->mapping. As reported by Sam Sun, this is the race that can occur:

CPU0: failed completion CPU1: final completion CPU2: truncate ----------------------- ---------------------- -------------- read_bytes_pending -= len finished = false / preempted before fserror_report_io() / read_bytes_pending -= len finished = true folio_end_read() truncate clears folio->mapping fserror_report_io( folio->mapping->host, ...) ^ NULL deref

Fix this by reporting the error first before decrementing ifs->read_bytes_pending.

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-53165"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-476"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-06-25T09:16:33Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\niomap: avoid potential null folio-\u003emapping deref during error reporting\n\nWhen a buffered read fails, iomap_finish_folio_read() reports the error\nwith fserror_report_io(folio-\u003emapping-\u003ehost, ...). This is called after\nifs-\u003eread_bytes_pending has been decremented by the bytes attempted to\nbe read.\n\nFor a folio split across multiple read completions, the folio is only\nguaranteed to stay locked while read_bytes_pending \u003e 0. Once\niomap_finish_folio_read() decrements read_bytes_pending, another\nin-flight read can complete and end the read on the folio, which unlocks\nit. This allows truncate logic to run and detach the folio (set\nfolio-\u003emapping to NULL). The error reporting path then can dereference a\nNULL folio-\u003emapping. As reported by Sam Sun, this is the race that can\noccur:\n\nCPU0: failed completion      CPU1: final completion     CPU2: truncate\n-----------------------      ----------------------     --------------\nread_bytes_pending -= len\nfinished = false\n/* preempted before\n   fserror_report_io() */\n\t\t\t     read_bytes_pending -= len\n\t\t\t     finished = true\n\t\t\t     folio_end_read()\n\t\t\t\t\t\t\ttruncate clears\n\t\t\t\t\t\t\tfolio-\u003emapping\nfserror_report_io(\n  folio-\u003emapping-\u003ehost, ...)\n\t      ^ NULL deref\n\nFix this by reporting the error first before decrementing\nifs-\u003eread_bytes_pending.",
  "id": "GHSA-f5cm-4mmf-92c9",
  "modified": "2026-06-28T09:31:42Z",
  "published": "2026-06-25T09:31:19Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53165"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1ad453817a4077230d1ba88eb0868f05f824449a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2eea7f44b9c8b42fd7d3a1a87c06a7cd1b99c327"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-53165 (GCVE-0-2026-53165)

Vulnerability from cvelistv5 – Published: 2026-06-25 08:38 – Updated: 2026-08-05 12:33

Title

iomap: avoid potential null folio->mapping deref during error reporting

Summary

In the Linux kernel, the following vulnerability has been resolved: iomap: avoid potential null folio->mapping deref during error reporting When a buffered read fails, iomap_finish_folio_read() reports the error with fserror_report_io(folio->mapping->host, ...). This is called after ifs->read_bytes_pending has been decremented by the bytes attempted to be read. For a folio split across multiple read completions, the folio is only guaranteed to stay locked while read_bytes_pending > 0. Once iomap_finish_folio_read() decrements read_bytes_pending, another in-flight read can complete and end the read on the folio, which unlocks it. This allows truncate logic to run and detach the folio (set folio->mapping to NULL). The error reporting path then can dereference a NULL folio->mapping. As reported by Sam Sun, this is the race that can occur: CPU0: failed completion CPU1: final completion CPU2: truncate ----------------------- ---------------------- -------------- read_bytes_pending -= len finished = false /* preempted before fserror_report_io() */ read_bytes_pending -= len finished = true folio_end_read() truncate clears folio->mapping fserror_report_io( folio->mapping->host, ...) ^ NULL deref Fix this by reporting the error first before decrementing ifs->read_bytes_pending.

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Assigner

Linux mitre root

References

2 references

URL	Tags
https://git.kernel.org/stable/c/1ad453817a4077230…
https://git.kernel.org/stable/c/2eea7f44b9c8b42fd…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: a9d573ee88af980f14fdadb5c12bbf6a195fb3f1 , < 1ad453817a4077230d1ba88eb0868f05f824449a (git) Affected: a9d573ee88af980f14fdadb5c12bbf6a195fb3f1 , < 2eea7f44b9c8b42fd7d3a1a87c06a7cd1b99c327 (git)
Linux	Linux	Affected: 7.0 Unaffected: 0 , < 7.0 (semver) Unaffected: 7.0.13 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/iomap/buffered-io.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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              "versionType": "git"
            },
            {
              "lessThan": "2eea7f44b9c8b42fd7d3a1a87c06a7cd1b99c327",
              "status": "affected",
              "version": "a9d573ee88af980f14fdadb5c12bbf6a195fb3f1",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/iomap/buffered-io.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.0"
            },
            {
              "lessThan": "7.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.13",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
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      ],
      "cpeApplicability": [
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          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
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                  "vulnerable": true
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              "negate": false,
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niomap: avoid potential null folio-\u003emapping deref during error reporting\n\nWhen a buffered read fails, iomap_finish_folio_read() reports the error\nwith fserror_report_io(folio-\u003emapping-\u003ehost, ...). This is called after\nifs-\u003eread_bytes_pending has been decremented by the bytes attempted to\nbe read.\n\nFor a folio split across multiple read completions, the folio is only\nguaranteed to stay locked while read_bytes_pending \u003e 0. Once\niomap_finish_folio_read() decrements read_bytes_pending, another\nin-flight read can complete and end the read on the folio, which unlocks\nit. This allows truncate logic to run and detach the folio (set\nfolio-\u003emapping to NULL). The error reporting path then can dereference a\nNULL folio-\u003emapping. As reported by Sam Sun, this is the race that can\noccur:\n\nCPU0: failed completion      CPU1: final completion     CPU2: truncate\n-----------------------      ----------------------     --------------\nread_bytes_pending -= len\nfinished = false\n/* preempted before\n   fserror_report_io() */\n\t\t\t     read_bytes_pending -= len\n\t\t\t     finished = true\n\t\t\t     folio_end_read()\n\t\t\t\t\t\t\ttruncate clears\n\t\t\t\t\t\t\tfolio-\u003emapping\nfserror_report_io(\n  folio-\u003emapping-\u003ehost, ...)\n\t      ^ NULL deref\n\nFix this by reporting the error first before decrementing\nifs-\u003eread_bytes_pending."
        }
      ],
      "metrics": [
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            "baseScore": 7.5,
            "baseSeverity": "HIGH",
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            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - Remote file-serving paths such as ksmbd and nfsd can drive VFS reads and truncates on iomap-backed filesystems, reaching the vulnerable completion path through network requests. A local syscall path also exists, but the highest reasonable exposure is a writable network share/export.\nAC:L - The bug is a race, but an attacker can issue concurrent read/readahead and truncate or size-change operations and retry the window. There is no memory-layout prerequisite, and uncertainty is resolved toward the higher-severity AC:L.\nPR:N - A writable anonymous or guest SMB/NFS export can expose the read and truncate operations without prior authentication. If the export requires credentials this would be PR:L, but the highest reasonable deployment is unauthenticated access.\nUI:N - The attacker can trigger both the read/error-reporting side and the truncate side directly through requests. No separate victim action is required.\nS:U - The fault occurs within the kernel filesystem/page-cache security authority. It does not cross a VM, IOMMU, or sandbox boundary.\nC:N - The vulnerable dereference is a NULL folio-\u003emapping dereference during error reporting. This is a crash condition, not an information disclosure primitive.\nI:N - The bug does not corrupt attacker-controlled memory or provide a write primitive. It only dereferences a NULL mapping pointer.\nA:H - A NULL pointer dereference in kernel context can oops or panic the system. Repeated triggering can deny availability of the affected host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:33:38.251Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/2eea7f44b9c8b42fd7d3a1a87c06a7cd1b99c327"
        }
      ],
      "title": "iomap: avoid potential null folio-\u003emapping deref during error reporting",
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        "engine": "bippy-1.2.0"
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-53165",
    "datePublished": "2026-06-25T08:38:45.445Z",
    "dateReserved": "2026-06-09T07:44:35.389Z",
    "dateUpdated": "2026-08-05T12:33:38.251Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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