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GHSA-FMWW-FWC4-2Q32

Vulnerability from github – Published: 2026-07-25 12:31 – Updated: 2026-07-25 12:31

Details

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

mm: shrinker: fix NULL pointer dereference in debugfs

shrinker_debugfs_add() creates both "count" and "scan" debugfs files unconditionally.

That assumes every shrinker implements both count_objects() and scan_objects(), which is not guaranteed. For example, the xen-backend shrinker sets count_objects() but leaves scan_objects() NULL, so writing to its scan file calls through a NULL function pointer and panics the kernel:

BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: 0010:0x0 Code: Unable to access opcode bytes at 0xffffffffffffffd6. Call Trace: shrinker_debugfs_scan_write+0x12e/0x270 full_proxy_write+0x5f/0x90 vfs_write+0xde/0x420 ? filp_flush+0x75/0x90 ? filp_close+0x1d/0x30 ? do_dup2+0xb8/0x120 ksys_write+0x68/0xf0 ? filp_flush+0x75/0x90 do_syscall_64+0xb3/0x5b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

The count path has the same issue in principle if a shrinker omits count_objects().

To fix it, only create "count" and "scan" debugfs files when the corresponding callbacks are present.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-64417"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-25T10:17:25Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: shrinker: fix NULL pointer dereference in debugfs\n\nshrinker_debugfs_add() creates both \"count\" and \"scan\" debugfs files\nunconditionally.\n\nThat assumes every shrinker implements both count_objects() and\nscan_objects(), which is not guaranteed.  For example, the xen-backend\nshrinker sets count_objects() but leaves scan_objects() NULL, so writing\nto its scan file calls through a NULL function pointer and panics the\nkernel:\n\nBUG: kernel NULL pointer dereference, address: 0000000000000000\nRIP: 0010:0x0\nCode: Unable to access opcode bytes at 0xffffffffffffffd6.\nCall Trace:\n \u003cTASK\u003e\n shrinker_debugfs_scan_write+0x12e/0x270\n full_proxy_write+0x5f/0x90\n vfs_write+0xde/0x420\n ? filp_flush+0x75/0x90\n ? filp_close+0x1d/0x30\n ? do_dup2+0xb8/0x120\n ksys_write+0x68/0xf0\n ? filp_flush+0x75/0x90\n do_syscall_64+0xb3/0x5b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nThe count path has the same issue in principle if a shrinker omits\ncount_objects().\n\nTo fix it, only create \"count\" and \"scan\" debugfs files when the\ncorresponding callbacks are present.",
  "id": "GHSA-fmww-fwc4-2q32",
  "modified": "2026-07-25T12:31:34Z",
  "published": "2026-07-25T12:31:34Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64417"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/006467ab932698612398f853344a7405164541f4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/09d2407985b8ce3e831f9d4310fe7ac06a6b3ae9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/36f8534f461222291a74156ab91f3ba9f09b6f93"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b9beed2322f3538b0d2d53307062da4102b8d8d8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e30453c61e185e914fde83c650e268067b140218"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ebb45c2648b1f60715fd283700f651e05e431231"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-64417 (GCVE-0-2026-64417)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-07-25 08:50

Title

mm: shrinker: fix NULL pointer dereference in debugfs

Summary

In the Linux kernel, the following vulnerability has been resolved: mm: shrinker: fix NULL pointer dereference in debugfs shrinker_debugfs_add() creates both "count" and "scan" debugfs files unconditionally. That assumes every shrinker implements both count_objects() and scan_objects(), which is not guaranteed. For example, the xen-backend shrinker sets count_objects() but leaves scan_objects() NULL, so writing to its scan file calls through a NULL function pointer and panics the kernel: BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: 0010:0x0 Code: Unable to access opcode bytes at 0xffffffffffffffd6. Call Trace: <TASK> shrinker_debugfs_scan_write+0x12e/0x270 full_proxy_write+0x5f/0x90 vfs_write+0xde/0x420 ? filp_flush+0x75/0x90 ? filp_close+0x1d/0x30 ? do_dup2+0xb8/0x120 ksys_write+0x68/0xf0 ? filp_flush+0x75/0x90 do_syscall_64+0xb3/0x5b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e The count path has the same issue in principle if a shrinker omits count_objects(). To fix it, only create "count" and "scan" debugfs files when the corresponding callbacks are present.

Severity

No CVSS data available.

Assigner

Linux

References

6 references

URL	Tags
https://git.kernel.org/stable/c/ebb45c2648b1f6071…
https://git.kernel.org/stable/c/09d2407985b8ce3e8…
https://git.kernel.org/stable/c/36f8534f461222291…
https://git.kernel.org/stable/c/006467ab932698612…
https://git.kernel.org/stable/c/b9beed2322f3538b0…
https://git.kernel.org/stable/c/e30453c61e185e914…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: bbf535fd6f06b94b9d07ed6f09397a936d4a58d8 , < ebb45c2648b1f60715fd283700f651e05e431231 (git) Affected: bbf535fd6f06b94b9d07ed6f09397a936d4a58d8 , < 09d2407985b8ce3e831f9d4310fe7ac06a6b3ae9 (git) Affected: bbf535fd6f06b94b9d07ed6f09397a936d4a58d8 , < 36f8534f461222291a74156ab91f3ba9f09b6f93 (git) Affected: bbf535fd6f06b94b9d07ed6f09397a936d4a58d8 , < 006467ab932698612398f853344a7405164541f4 (git) Affected: bbf535fd6f06b94b9d07ed6f09397a936d4a58d8 , < b9beed2322f3538b0d2d53307062da4102b8d8d8 (git) Affected: bbf535fd6f06b94b9d07ed6f09397a936d4a58d8 , < e30453c61e185e914fde83c650e268067b140218 (git)
Linux	Linux	Affected: 6.0 Unaffected: 0 , < 6.0 (semver) Unaffected: 6.1.178 , ≤ 6.1.* (semver) Unaffected: 6.6.145 , ≤ 6.6.* (semver) Unaffected: 6.12.96 , ≤ 6.12.* (semver) Unaffected: 6.18.39 , ≤ 6.18.* (semver) Unaffected: 7.1.4 , ≤ 7.1.* (semver) Unaffected: 7.2-rc3 , ≤ * (original_commit_for_fix)

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          "programFiles": [
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              "versionType": "semver"
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              "status": "unaffected",
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.12.96",
              "versionType": "semver"
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              "versionType": "semver"
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              "version": "7.1.4",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc3",
              "versionType": "original_commit_for_fix"
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          ]
        }
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        }
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    "datePublished": "2026-07-25T08:50:56.800Z",
    "dateReserved": "2026-07-19T15:36:31.786Z",
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}

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.

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GHSA-FMWW-FWC4-2Q32

CVE-2026-64417 (GCVE-0-2026-64417)

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Sightings

Nomenclature