{"id":"CVE-2026-68138","summary":"net/sched: serialize qdisc_rtab_list against concurrent get/put","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: serialize qdisc_rtab_list against concurrent get/put\n\nqdisc_get_rtab() and qdisc_put_rtab() mutate the process-global singly\nlinked list qdisc_rtab_list and a plain non-atomic 'int refcnt' with no\nlock. This was only safe because every caller historically held the RTNL\nmutex, which serialized all rate-table lookups, inserts and frees.\n\nThat invariant no longer holds. cls_flower sets\nTCF_PROTO_OPS_DOIT_UNLOCKED, so tc_new_tfilter() keeps rtnl_held == false\nfor it and sets TCA_ACT_FLAGS_NO_RTNL. That flag propagates through\ntcf_exts_validate_ex() -\u003e tcf_action_init() -\u003e tcf_action_init_1() -\u003e\ntcf_police_init(), which calls qdisc_get_rtab()/qdisc_put_rtab() with the\nRTNL mutex NOT held. Two RTM_NEWTFILTER requests on different CPUs, each\nadding a flower filter with a police action carrying the same rate, then\nrace on qdisc_rtab_list and on the non-atomic refcnt, leading to a\nuse-after-free / double-free of the kmalloc-2k struct qdisc_rate_table.\nqdisc_rtab_list is a single global (not per-netns), so the corrupted\nobject is shared system-wide.\n\n  BUG: KASAN: slab-use-after-free in qdisc_put_rtab+0x12f/0x160\n   qdisc_put_rtab+0x12f/0x160\n   tcf_police_init+0xda9/0x1590\n   tcf_action_init_1+0x460/0x6b0\n   tcf_action_init+0x439/0xa40\n   tcf_exts_validate_ex+0x42d/0x550\n   fl_change+0xddd/0x7da0\n   tc_new_tfilter+0xaa7/0x2420\n   rtnetlink_rcv_msg+0x95e/0xe90\n  which belongs to the cache kmalloc-2k of size 2048\n\nProtect qdisc_rtab_list and the refcount with a dedicated spinlock. The\n(sleeping, GFP_KERNEL) allocation in qdisc_get_rtab() is performed before\ntaking the lock; if a concurrent inserter added an identical table in the\nmeantime the freshly allocated one is freed under the lock, so no\nduplicate is leaked. qdisc_put_rtab() now decrements the refcount and\nunlinks under the same lock.","modified":"2026-09-30T18:26:50.030764333Z","published":"2026-08-10T11:59:01.744Z","related":["SUSE-SU-2026:23477-1","SUSE-SU-2026:23481-1","SUSE-SU-2026:23528-1","SUSE-SU-2026:23529-1","SUSE-SU-2026:23672-1","SUSE-SU-2026:23673-1","SUSE-SU-2026:23674-1","SUSE-SU-2026:23675-1","SUSE-SU-2026:23676-1","SUSE-SU-2026:23677-1","SUSE-SU-2026:23678-1","SUSE-SU-2026:23679-1","SUSE-SU-2026:23680-1","SUSE-SU-2026:23681-1","SUSE-SU-2026:23682-1","SUSE-SU-2026:23683-1","SUSE-SU-2026:23684-1","SUSE-SU-2026:23685-1","SUSE-SU-2026:23686-1","SUSE-SU-2026:23687-1","SUSE-SU-2026:23747-1","SUSE-SU-2026:23748-1","SUSE-SU-2026:23749-1","SUSE-SU-2026:23750-1","SUSE-SU-2026:23751-1","SUSE-SU-2026:23752-1","SUSE-SU-2026:23753-1","SUSE-SU-2026:23754-1","SUSE-SU-2026:23755-1","SUSE-SU-2026:23756-1","SUSE-SU-2026:23757-1","SUSE-SU-2026:23758-1","SUSE-SU-2026:23759-1","SUSE-SU-2026:23760-1","SUSE-SU-2026:23761-1","SUSE-SU-2026:23762-1","SUSE-SU-2026:23763-1","SUSE-SU-2026:23764-1","SUSE-SU-2026:23766-1","SUSE-SU-2026:23767-1","SUSE-SU-2026:23768-1","SUSE-SU-2026:23769-1","SUSE-SU-2026:23770-1","SUSE-SU-2026:23771-1","SUSE-SU-2026:23772-1","SUSE-SU-2026:23773-1","SUSE-SU-2026:23774-1","SUSE-SU-2026:23775-1","SUSE-SU-2026:23776-1","SUSE-SU-2026:23777-1","SUSE-SU-2026:23778-1","SUSE-SU-2026:23779-1","SUSE-SU-2026:23780-1","SUSE-SU-2026:23781-1","SUSE-SU-2026:23789-1","SUSE-SU-2026:23790-1","SUSE-SU-2026:23791-1","SUSE-SU-2026:23797-1","SUSE-SU-2026:23798-1","SUSE-SU-2026:23799-1","SUSE-SU-2026:23801-1","SUSE-SU-2026:23803-1","SUSE-SU-2026:23804-1","SUSE-SU-2026:23805-1","SUSE-SU-2026:23806-1","SUSE-SU-2026:23807-1","SUSE-SU-2026:23808-1","SUSE-SU-2026:23809-1","SUSE-SU-2026:23810-1","SUSE-SU-2026:23811-1","SUSE-SU-2026:23812-1","SUSE-SU-2026:23813-1","SUSE-SU-2026:23814-1","SUSE-SU-2026:23815-1","SUSE-SU-2026:23816-1","SUSE-SU-2026:23817-1","SUSE-SU-2026:23818-1","SUSE-SU-2026:23819-1","SUSE-SU-2026:23820-1","SUSE-SU-2026:23821-1","SUSE-SU-2026:23822-1","SUSE-SU-2026:23823-1","SUSE-SU-2026:23824-1","SUSE-SU-2026:23825-1","SUSE-SU-2026:23826-1","SUSE-SU-2026:23827-1","SUSE-SU-2026:23828-1","SUSE-SU-2026:23832-1","SUSE-SU-2026:23833-1","SUSE-SU-2026:23834-1","SUSE-SU-2026:23835-1","SUSE-SU-2026:23836-1","SUSE-SU-2026:23837-1","SUSE-SU-2026:23838-1","SUSE-SU-2026:23839-1","SUSE-SU-2026:23881-1","SUSE-SU-2026:23887-1","SUSE-SU-2026:23897-1","SUSE-SU-2026:23902-1","SUSE-SU-2026:4120-1","SUSE-SU-2026:4168-1","SUSE-SU-2026:4170-1","SUSE-SU-2026:4172-1","SUSE-SU-2026:4183-1","SUSE-SU-2026:4185-1","SUSE-SU-2026:4193-1","SUSE-SU-2026:4231-1","SUSE-SU-2026:4244-1","SUSE-SU-2026:4254-1","SUSE-SU-2026:4255-1","SUSE-SU-2026:4256-1","SUSE-SU-2026:4258-1","SUSE-SU-2026:4259-1","SUSE-SU-2026:4279-1","SUSE-SU-2026:4284-1","SUSE-SU-2026:4315-1","SUSE-SU-2026:4347-1","SUSE-SU-2026:4356-1","SUSE-SU-2026:4357-1","SUSE-SU-2026:4359-1","SUSE-SU-2026:4369-1","SUSE-SU-2026:4383-1","openSUSE-SU-2026:21910-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68138.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/1b050d09dd1a0ddae83bf012cf4956b7a960235f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4131dd0b6f67acddd616ed7c244e1d3eedd46e7b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6e0241f6cbb149d926ee8efee2c734fea71452cf"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8ddc2eb0d2da9c83f54f1e5720525b461b8480c4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d981098b76756ed71666a27518eeb69883657c43"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f43ee0c0730d6191629b5ee1ceae27b1ebfdc047"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f93c89392bd3b180b5b7abc6fdae8e3dd667a313"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fb29e1b41052488ee3f2d115d4a870497ebd7f7d"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68138.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68138"},{"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":"470502de5bdb1ed0def643a4458593a40b8f6b66"},{"fixed":"1b050d09dd1a0ddae83bf012cf4956b7a960235f"},{"fixed":"6e0241f6cbb149d926ee8efee2c734fea71452cf"},{"fixed":"f93c89392bd3b180b5b7abc6fdae8e3dd667a313"},{"fixed":"4131dd0b6f67acddd616ed7c244e1d3eedd46e7b"},{"fixed":"d981098b76756ed71666a27518eeb69883657c43"},{"fixed":"8ddc2eb0d2da9c83f54f1e5720525b461b8480c4"},{"fixed":"fb29e1b41052488ee3f2d115d4a870497ebd7f7d"},{"fixed":"f43ee0c0730d6191629b5ee1ceae27b1ebfdc047"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68138.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.1.0"},{"fixed":"5.10.266"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.217"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.184"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.153"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.105"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.46"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68138.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}