FKIE_CVE-2026-64417

Vulnerability from fkie_nvd - Published: 2026-07-25 10:17 - Updated: 2026-07-25 10:17
Severity
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/006467ab932698612398f853344a7405164541f4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/09d2407985b8ce3e831f9d4310fe7ac06a6b3ae9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/36f8534f461222291a74156ab91f3ba9f09b6f93
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b9beed2322f3538b0d2d53307062da4102b8d8d8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e30453c61e185e914fde83c650e268067b140218
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ebb45c2648b1f60715fd283700f651e05e431231
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "mm/shrinker_debug.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "ebb45c2648b1f60715fd283700f651e05e431231",
              "status": "affected",
              "version": "bbf535fd6f06b94b9d07ed6f09397a936d4a58d8",
              "versionType": "git"
            },
            {
              "lessThan": "09d2407985b8ce3e831f9d4310fe7ac06a6b3ae9",
              "status": "affected",
              "version": "bbf535fd6f06b94b9d07ed6f09397a936d4a58d8",
              "versionType": "git"
            },
            {
              "lessThan": "36f8534f461222291a74156ab91f3ba9f09b6f93",
              "status": "affected",
              "version": "bbf535fd6f06b94b9d07ed6f09397a936d4a58d8",
              "versionType": "git"
            },
            {
              "lessThan": "006467ab932698612398f853344a7405164541f4",
              "status": "affected",
              "version": "bbf535fd6f06b94b9d07ed6f09397a936d4a58d8",
              "versionType": "git"
            },
            {
              "lessThan": "b9beed2322f3538b0d2d53307062da4102b8d8d8",
              "status": "affected",
              "version": "bbf535fd6f06b94b9d07ed6f09397a936d4a58d8",
              "versionType": "git"
            },
            {
              "lessThan": "e30453c61e185e914fde83c650e268067b140218",
              "status": "affected",
              "version": "bbf535fd6f06b94b9d07ed6f09397a936d4a58d8",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "mm/shrinker_debug.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.0"
            },
            {
              "lessThan": "6.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.178",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.145",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.96",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.39",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc3",
              "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\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": "CVE-2026-64417",
  "lastModified": "2026-07-25T10:17:25.567",
  "metrics": {},
  "published": "2026-07-25T10:17:25.567",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/006467ab932698612398f853344a7405164541f4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/09d2407985b8ce3e831f9d4310fe7ac06a6b3ae9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/36f8534f461222291a74156ab91f3ba9f09b6f93"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b9beed2322f3538b0d2d53307062da4102b8d8d8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e30453c61e185e914fde83c650e268067b140218"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ebb45c2648b1f60715fd283700f651e05e431231"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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