CVE-2026-90248 (GCVE-0-2026-90248)
Vulnerability from cvelistv5
Published
2026-09-17 16:07
Modified
2026-10-19 09:00
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_api: fix teardown of an adopted proto on insert-race loss In tc_new_tfilter() the create branch sets tp_created = 1 before calling tcf_chain_tp_insert_unique(). When the caller loses the race (another request inserted a proto at the same chain/prio first), insert_unique() destroys the caller's own tp_new and returns the winner's proto with an extra reference. tp_created was never cleared, so the loser's errout path treated the winner's live proto as its own and called tcf_chain_tp_delete_empty() on it, silently unlinking an active classifier that the winning request already advertised via RTM_NEWTFILTER. Track the outcome of the insert step in a single tri-state variable so each errout path reacts correctly: - TP_NOT_CREATED: no proto created; pursue the old path. - TP_CREATED: proto inserted successfully; same code path as before. - TP_NOT_OWNED: New - lost the insert race; tp is another request's proto (chain ref already released by tp_new's destroy) Both errout reactions are single expressions derived from the state. This fix is motivated by the Sashiko's automated review of Patch (net/sched: cls_api: Always acquire rtnl_lock when destroying locked classifiers) [1][2]. The review identified the silent-unlink behaviour of an adopted proto's teardown when a request loses the tcf_chain_tp_insert_unique() race. [1] https://sashiko.dev/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com [2] https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com
References
Impacted products
Vendor Product Version
Linux Linux Version: 8b64678e0af8f4d62a40149baedebe78503a5255
Version: 8b64678e0af8f4d62a40149baedebe78503a5255
Version: 8b64678e0af8f4d62a40149baedebe78503a5255
Version: 8b64678e0af8f4d62a40149baedebe78503a5255
Version: 8b64678e0af8f4d62a40149baedebe78503a5255
Version: 8b64678e0af8f4d62a40149baedebe78503a5255
Version: 8b64678e0af8f4d62a40149baedebe78503a5255
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_api: fix teardown of an adopted proto on insert-race loss\n\nIn tc_new_tfilter() the create branch sets tp_created = 1 before calling\ntcf_chain_tp_insert_unique(). When the caller loses the race (another\nrequest inserted a proto at the same chain/prio first), insert_unique()\ndestroys the caller\u0027s own tp_new and returns the winner\u0027s proto with an\nextra reference. tp_created was never cleared, so the loser\u0027s errout\npath treated the winner\u0027s live proto as its own and called\ntcf_chain_tp_delete_empty() on it, silently unlinking an active\nclassifier that the winning request already advertised via\nRTM_NEWTFILTER.\n\nTrack the outcome of the insert step in a single tri-state variable so\neach errout path reacts correctly:\n\n- TP_NOT_CREATED: no proto created; pursue the old path.\n- TP_CREATED: proto inserted successfully; same code path as before.\n- TP_NOT_OWNED: New - lost the insert race; tp is another request\u0027s proto\n  (chain ref already released by tp_new\u0027s destroy)\n\nBoth errout reactions are single expressions derived from the state.\n\nThis fix is motivated by the Sashiko\u0027s automated review of Patch\n(net/sched: cls_api: Always acquire rtnl_lock when destroying locked\nclassifiers) [1][2]. The review identified the silent-unlink behaviour of\nan adopted proto\u0027s teardown when a request loses the\ntcf_chain_tp_insert_unique() race.\n\n[1] https://sashiko.dev/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com\n[2] https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:00:24.022Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a68e664ddf16ecae6d769d6a2eb356f8abab75c9"
        },
        {
          "url": "https://git.kernel.org/stable/c/df02b6dc136af45e92ee4c86f4aa6c9a60790b1e"
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        {
          "url": "https://git.kernel.org/stable/c/bee2208276c8e0e40a249ffdcf6e5434a79a847c"
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          "url": "https://git.kernel.org/stable/c/219c87aeefdcc8c1caf28cc99e9b361ce7393d3a"
        },
        {
          "url": "https://git.kernel.org/stable/c/bbe2fd6d77df630356185406a97317f6aa6a92cf"
        },
        {
          "url": "https://git.kernel.org/stable/c/dc8b33b819cb02a75936940c120aa669ad89942d"
        },
        {
          "url": "https://git.kernel.org/stable/c/d4e359b3608a0e184bbe8d61a5c3b50d0831c44a"
        }
      ],
      "title": "net/sched: cls_api: fix teardown of an adopted proto on insert-race loss",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90248",
    "datePublished": "2026-09-17T16:07:50.104Z",
    "dateReserved": "2026-09-11T19:38:34.795Z",
    "dateUpdated": "2026-10-19T09:00:24.022Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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