{"id":"CVE-2026-90248","summary":"net/sched: cls_api: fix teardown of an adopted proto on insert-race loss","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's own tp_new and returns the winner's proto with an\nextra reference. tp_created was never cleared, so the loser's errout\npath treated the winner's 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's proto\n  (chain ref already released by tp_new's destroy)\n\nBoth errout reactions are single expressions derived from the state.\n\nThis fix is motivated by the Sashiko's 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's 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","modified":"2026-09-19T03:47:25.481881152Z","published":"2026-09-17T16:07:50.104Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90248.json"},"references":[{"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"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90248.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90248"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"8b64678e0af8f4d62a40149baedebe78503a5255"},{"fixed":"a68e664ddf16ecae6d769d6a2eb356f8abab75c9"},{"fixed":"df02b6dc136af45e92ee4c86f4aa6c9a60790b1e"},{"fixed":"bee2208276c8e0e40a249ffdcf6e5434a79a847c"},{"fixed":"219c87aeefdcc8c1caf28cc99e9b361ce7393d3a"},{"fixed":"bbe2fd6d77df630356185406a97317f6aa6a92cf"},{"fixed":"dc8b33b819cb02a75936940c120aa669ad89942d"},{"fixed":"d4e359b3608a0e184bbe8d61a5c3b50d0831c44a"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90248.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.1.0"},{"fixed":"5.15.221"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.188"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.157"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.110"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.52"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90248.json"}}],"schema_version":"1.9.0"}