GHSA-RM9P-RR32-F7J6
Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-09-17 18:31In 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
{
"affected": [],
"aliases": [
"CVE-2026-90248"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:17:20Z",
"severity": null
},
"details": "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",
"id": "GHSA-rm9p-rr32-f7j6",
"modified": "2026-09-17T18:31:57Z",
"published": "2026-09-17T18:31:57Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90248"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/219c87aeefdcc8c1caf28cc99e9b361ce7393d3a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a68e664ddf16ecae6d769d6a2eb356f8abab75c9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bbe2fd6d77df630356185406a97317f6aa6a92cf"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bee2208276c8e0e40a249ffdcf6e5434a79a847c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d4e359b3608a0e184bbe8d61a5c3b50d0831c44a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dc8b33b819cb02a75936940c120aa669ad89942d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/df02b6dc136af45e92ee4c86f4aa6c9a60790b1e"
}
],
"schema_version": "1.4.0",
"severity": []
}
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