ghsa-546w-ffx9-gj3g
Vulnerability from github
Published
2025-07-10 09:32
Modified
2025-07-10 09:32
Details

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

kernfs: Relax constraint in draining guard

The active reference lifecycle provides the break/unbreak mechanism but the active reference is not truly active after unbreak -- callers don't use it afterwards but it's important for proper pairing of kn->active counting. Assuming this mechanism is in place, the WARN check in kernfs_should_drain_open_files() is too sensitive -- it may transiently catch those (rightful) callers between kernfs_unbreak_active_protection() and kernfs_put_active() as found out by Chen Ridong:

kernfs_remove_by_name_ns    kernfs_get_active // active=1
__kernfs_remove                   // active=0x80000002
kernfs_drain            ...
wait_event
//waiting (active == 0x80000001)
                kernfs_break_active_protection
                // active = 0x80000001
// continue
                kernfs_unbreak_active_protection
                // active = 0x80000002
...
kernfs_should_drain_open_files
// warning occurs
                kernfs_put_active

To avoid the false positives (mind panic_on_warn) remove the check altogether. (This is meant as quick fix, I think active reference break/unbreak may be simplified with larger rework.)

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{
  "affected": [],
  "aliases": [
    "CVE-2025-38282"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-07-10T08:15:26Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nkernfs: Relax constraint in draining guard\n\nThe active reference lifecycle provides the break/unbreak mechanism but\nthe active reference is not truly active after unbreak -- callers don\u0027t\nuse it afterwards but it\u0027s important for proper pairing of kn-\u003eactive\ncounting. Assuming this mechanism is in place, the WARN check in\nkernfs_should_drain_open_files() is too sensitive -- it may transiently\ncatch those (rightful) callers between\nkernfs_unbreak_active_protection() and kernfs_put_active() as found out by Chen\nRidong:\n\n\tkernfs_remove_by_name_ns\tkernfs_get_active // active=1\n\t__kernfs_remove\t\t\t\t\t  // active=0x80000002\n\tkernfs_drain\t\t\t...\n\twait_event\n\t//waiting (active == 0x80000001)\n\t\t\t\t\tkernfs_break_active_protection\n\t\t\t\t\t// active = 0x80000001\n\t// continue\n\t\t\t\t\tkernfs_unbreak_active_protection\n\t\t\t\t\t// active = 0x80000002\n\t...\n\tkernfs_should_drain_open_files\n\t// warning occurs\n\t\t\t\t\tkernfs_put_active\n\nTo avoid the false positives (mind panic_on_warn) remove the check altogether.\n(This is meant as quick fix, I think active reference break/unbreak may be\nsimplified with larger rework.)",
  "id": "GHSA-546w-ffx9-gj3g",
  "modified": "2025-07-10T09:32:29Z",
  "published": "2025-07-10T09:32:29Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38282"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/071d8e4c2a3b0999a9b822e2eb8854784a350f8a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2d6a67c2b3b87808a347dc1047b520a9dd177a4f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6bfb154f95d5f0ab7ed056f23aba8c1a94cb3927"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6c81f1c7812c61f187bed1b938f1d2e391d503ab"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/72275c888f8962b406ee9c6885c79bf68cca5a63"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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