ghsa-rpg5-5rc2-v629
Vulnerability from github
Published
2025-08-22 18:31
Modified
2025-08-22 18:31
Details

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

pinmux: fix race causing mux_owner NULL with active mux_usecount

commit 5a3e85c3c397 ("pinmux: Use sequential access to access desc->pinmux data") tried to address the issue when two client of the same gpio calls pinctrl_select_state() for the same functionality, was resulting in NULL pointer issue while accessing desc->mux_owner. However, issue was not completely fixed due to the way it was handled and it can still result in the same NULL pointer.

The issue occurs due to the following interleaving:

 cpu0 (process A)                   cpu1 (process B)

  pin_request() {                   pin_free() {

                                     mutex_lock()
                                     desc->mux_usecount--; //becomes 0
                                     ..
                                     mutex_unlock()

mutex_lock(desc->mux) desc->mux_usecount++; // becomes 1 desc->mux_owner = owner; mutex_unlock(desc->mux)

                                     mutex_lock(desc->mux)
                                     desc->mux_owner = NULL;
                                     mutex_unlock(desc->mux)

This sequence leads to a state where the pin appears to be in use (mux_usecount == 1) but has no owner (mux_owner == NULL), which can cause NULL pointer on next pin_request on the same pin.

Ensure that updates to mux_usecount and mux_owner are performed atomically under the same lock. Only clear mux_owner when mux_usecount reaches zero and no new owner has been assigned.

Show details on source website

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{
  "affected": [],
  "aliases": [
    "CVE-2025-38632"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-08-22T16:15:37Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\npinmux: fix race causing mux_owner NULL with active mux_usecount\n\ncommit 5a3e85c3c397 (\"pinmux: Use sequential access to access\ndesc-\u003epinmux data\") tried to address the issue when two client of the\nsame gpio calls pinctrl_select_state() for the same functionality, was\nresulting in NULL pointer issue while accessing desc-\u003emux_owner.\nHowever, issue was not completely fixed due to the way it was handled\nand it can still result in the same NULL pointer.\n\nThe issue occurs due to the following interleaving:\n\n     cpu0 (process A)                   cpu1 (process B)\n\n      pin_request() {                   pin_free() {\n\n                                         mutex_lock()\n                                         desc-\u003emux_usecount--; //becomes 0\n                                         ..\n                                         mutex_unlock()\n\n  mutex_lock(desc-\u003emux)\n  desc-\u003emux_usecount++; // becomes 1\n  desc-\u003emux_owner = owner;\n  mutex_unlock(desc-\u003emux)\n\n                                         mutex_lock(desc-\u003emux)\n                                         desc-\u003emux_owner = NULL;\n                                         mutex_unlock(desc-\u003emux)\n\nThis sequence leads to a state where the pin appears to be in use\n(`mux_usecount == 1`) but has no owner (`mux_owner == NULL`), which can\ncause NULL pointer on next pin_request on the same pin.\n\nEnsure that updates to mux_usecount and mux_owner are performed\natomically under the same lock. Only clear mux_owner when mux_usecount\nreaches zero and no new owner has been assigned.",
  "id": "GHSA-rpg5-5rc2-v629",
  "modified": "2025-08-22T18:31:22Z",
  "published": "2025-08-22T18:31:22Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38632"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0b075c011032f88d1cfde3b45d6dcf08b44140eb"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/22b585cbd67d14df3b91529d1b990661c300faa9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9b2a3e7189028aa7c4d53a84364f2ea9fb209787"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9ea3f6b9a67be3476e331ce51cac316c2614a564"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b7bd6e3971eb7f0e34d2fdce1b18b08094e0c804"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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