CVE-2025-39905 (GCVE-0-2025-39905)
Vulnerability from cvelistv5
Published
2025-10-01 07:44
Modified
2025-10-01 07:44
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: net: phylink: add lock for serializing concurrent pl->phydev writes with resolver Currently phylink_resolve() protects itself against concurrent phylink_bringup_phy() or phylink_disconnect_phy() calls which modify pl->phydev by relying on pl->state_mutex. The problem is that in phylink_resolve(), pl->state_mutex is in a lock inversion state with pl->phydev->lock. So pl->phydev->lock needs to be acquired prior to pl->state_mutex. But that requires dereferencing pl->phydev in the first place, and without pl->state_mutex, that is racy. Hence the reason for the extra lock. Currently it is redundant, but it will serve a functional purpose once mutex_lock(&phy->lock) will be moved outside of the mutex_lock(&pl->state_mutex) section. Another alternative considered would have been to let phylink_resolve() acquire the rtnl_mutex, which is also held when phylink_bringup_phy() and phylink_disconnect_phy() are called. But since phylink_disconnect_phy() runs under rtnl_lock(), it would deadlock with phylink_resolve() when calling flush_work(&pl->resolve). Additionally, it would have been undesirable because it would have unnecessarily blocked many other call paths as well in the entire kernel, so the smaller-scoped lock was preferred.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/phy/phylink.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"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "6.16.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
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                },
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              "negate": false,
              "operator": "OR"
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          ]
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: phylink: add lock for serializing concurrent pl-\u003ephydev writes with resolver\n\nCurrently phylink_resolve() protects itself against concurrent\nphylink_bringup_phy() or phylink_disconnect_phy() calls which modify\npl-\u003ephydev by relying on pl-\u003estate_mutex.\n\nThe problem is that in phylink_resolve(), pl-\u003estate_mutex is in a lock\ninversion state with pl-\u003ephydev-\u003elock. So pl-\u003ephydev-\u003elock needs to be\nacquired prior to pl-\u003estate_mutex. But that requires dereferencing\npl-\u003ephydev in the first place, and without pl-\u003estate_mutex, that is\nracy.\n\nHence the reason for the extra lock. Currently it is redundant, but it\nwill serve a functional purpose once mutex_lock(\u0026phy-\u003elock) will be\nmoved outside of the mutex_lock(\u0026pl-\u003estate_mutex) section.\n\nAnother alternative considered would have been to let phylink_resolve()\nacquire the rtnl_mutex, which is also held when phylink_bringup_phy()\nand phylink_disconnect_phy() are called. But since phylink_disconnect_phy()\nruns under rtnl_lock(), it would deadlock with phylink_resolve() when\ncalling flush_work(\u0026pl-\u003eresolve). Additionally, it would have been\nundesirable because it would have unnecessarily blocked many other call\npaths as well in the entire kernel, so the smaller-scoped lock was\npreferred."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-10-01T07:44:28.758Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/56fe63b05ec84ae6674269d78397cec43a7a295a"
        },
        {
          "url": "https://git.kernel.org/stable/c/0ba5b2f2c381dbec9ed9e4ab3ae5d3e667de0dc3"
        }
      ],
      "title": "net: phylink: add lock for serializing concurrent pl-\u003ephydev writes with resolver",
      "x_generator": {
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    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39905",
    "datePublished": "2025-10-01T07:44:28.758Z",
    "dateReserved": "2025-04-16T07:20:57.146Z",
    "dateUpdated": "2025-10-01T07:44:28.758Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-39905\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-10-01T08:15:33.370\",\"lastModified\":\"2025-10-02T19:12:17.160\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: phylink: add lock for serializing concurrent pl-\u003ephydev writes with resolver\\n\\nCurrently phylink_resolve() protects itself against concurrent\\nphylink_bringup_phy() or phylink_disconnect_phy() calls which modify\\npl-\u003ephydev by relying on pl-\u003estate_mutex.\\n\\nThe problem is that in phylink_resolve(), pl-\u003estate_mutex is in a lock\\ninversion state with pl-\u003ephydev-\u003elock. So pl-\u003ephydev-\u003elock needs to be\\nacquired prior to pl-\u003estate_mutex. But that requires dereferencing\\npl-\u003ephydev in the first place, and without pl-\u003estate_mutex, that is\\nracy.\\n\\nHence the reason for the extra lock. Currently it is redundant, but it\\nwill serve a functional purpose once mutex_lock(\u0026phy-\u003elock) will be\\nmoved outside of the mutex_lock(\u0026pl-\u003estate_mutex) section.\\n\\nAnother alternative considered would have been to let phylink_resolve()\\nacquire the rtnl_mutex, which is also held when phylink_bringup_phy()\\nand phylink_disconnect_phy() are called. But since phylink_disconnect_phy()\\nruns under rtnl_lock(), it would deadlock with phylink_resolve() when\\ncalling flush_work(\u0026pl-\u003eresolve). Additionally, it would have been\\nundesirable because it would have unnecessarily blocked many other call\\npaths as well in the entire kernel, so the smaller-scoped lock was\\npreferred.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0ba5b2f2c381dbec9ed9e4ab3ae5d3e667de0dc3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/56fe63b05ec84ae6674269d78397cec43a7a295a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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