{"id":"CVE-2026-74284","summary":"net/sched: sch_hfsc: Don't make class passive twice","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_hfsc: Don't make class passive twice\n\nupdate_vf() is called from two places for the same class during a single\ndequeue when the class's child qdisc (e.g. codel/fq_codel) drops its last\npackets while dequeuing:\n\n1. The child calls qdisc_tree_reduce_backlog(), which, now that the child\n   is empty, invokes hfsc_qlen_notify() -\u003e update_vf(cl, 0, 0) and turns\n   the class passive (cl_nactive is decremented up the hierarchy).\n\n2. hfsc_dequeue() then calls update_vf(cl, qdisc_pkt_len(skb), cur_time)\n   to charge the dequeued bytes.\n\nOn the second call the class is already passive, but its child qdisc is\nstill empty, so update_vf() arms go_passive again:\n\n      if (cl-\u003eqdisc-\u003eq.qlen == 0 && cl-\u003ecl_flags & HFSC_FSC)\n              go_passive = 1;\n\nThe leaf is then skipped by the cl_nactive == 0 check inside the loop,\nwhich does not clear go_passive, so the stale go_passive propagates to the\nparent and decrements its cl_nactive a second time. A parent that still\nhas other active children is driven to cl_nactive == 0 and removed from\nthe vttree, even though those siblings are still backlogged. They are\nnever dequeued again and the qdisc stalls.\n\nFix this by only arming go_passive when the class is actually active, so an\nalready-passive class no longer triggers a second passive transition. The\nbyte accounting (cl-\u003ecl_total += len) still runs for every ancestor, so\ndequeued bytes continue to be counted exactly once.","modified":"2026-10-28T02:30:21.575692274Z","published":"2026-08-15T05:57:53.290Z","related":["SUSE-SU-2026:23881-1","SUSE-SU-2026:23887-1","SUSE-SU-2026:23897-1","SUSE-SU-2026:23902-1","SUSE-SU-2026:24181-1","SUSE-SU-2026:24182-1","SUSE-SU-2026:24315-1","SUSE-SU-2026:24316-1","SUSE-SU-2026:4640-1","SUSE-SU-2026:4687-1","SUSE-SU-2026:4706-1","openSUSE-SU-2026:21910-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74284.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/15720cd8fa3fc625146128f89a8e11b0449a20a7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3a49bbae676fef1ffe548971e6229ae2adeb9d10"},{"type":"WEB","url":"https://git.kernel.org/stable/c/66dbb13eeb2fc339f8f548a9076be4c1a94857b0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/90b662ea25f5e83bb3b8ccec5b93ced810b92fb8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9221a594c72a1446137926d4c2aa04e345f798dc"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a425c82ff06cda5165e0de3de8c2a445ec1f863e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b2a017bfcf565721918ec7355a373911d2f2a227"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fc973ecd1a079b9a87c360478542f3a56dea085b"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74284.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74284"},{"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":"72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7"},{"fixed":"a425c82ff06cda5165e0de3de8c2a445ec1f863e"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"a5efc95a33bd4fcb879250852828cc58c7862970"},{"fixed":"fc973ecd1a079b9a87c360478542f3a56dea085b"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87"},{"fixed":"15720cd8fa3fc625146128f89a8e11b0449a20a7"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"9030a91235ae4845ec71902c3e0cecfc9ed1f2df"},{"fixed":"b2a017bfcf565721918ec7355a373911d2f2a227"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"d06476714d2819b550e0cc39222347e2c8941c9d"},{"fixed":"9221a594c72a1446137926d4c2aa04e345f798dc"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"51eb3b65544c9efd6a1026889ee5fb5aa62da3bb"},{"fixed":"66dbb13eeb2fc339f8f548a9076be4c1a94857b0"},{"fixed":"3a49bbae676fef1ffe548971e6229ae2adeb9d10"},{"fixed":"90b662ea25f5e83bb3b8ccec5b93ced810b92fb8"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5.10.241"},{"fixed":"5.10.261"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5.15.190"},{"fixed":"5.15.212"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.1.138"},{"fixed":"6.1.178"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.6.90"},{"fixed":"6.6.145"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.12.28"},{"fixed":"6.12.97"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5.4.297"},{"fixed":"5.5"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.14.6"},{"fixed":"6.15"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"9a5fd5c2f4d4afdd5e405083ee53e0789ce76956"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c1175c4ad01dbc9c979d099861fa90a754f72059"}]}],"versions":["v5.10.260","v5.10.259","v5.10.258","v5.10.257","v5.10.256","v5.10.255","v5.10.254","v5.10.253","v5.10.252","v5.10.251","v5.10.250","v5.10.249","v5.10.248","v5.10.247","v5.10.246","v5.10.245","v5.10.244","v5.10.243","v5.10.242","v5.10.241","v5.15.211","v5.15.210","v5.15.209","v5.15.208","v5.15.207","v5.15.206","v5.15.205","v5.15.204","v5.15.203","v5.15.202","v5.15.201","v5.15.200","v5.15.199","v5.15.198","v5.15.197","v5.15.196","v5.15.195","v5.15.194","v5.15.193","v5.15.192","v5.15.191","v5.15.190","v6.1.177","v6.1.176","v6.1.175","v6.1.174","v6.1.173","v6.1.172","v6.1.171","v6.1.170","v6.1.169","v6.1.168","v6.1.167","v6.1.166","v6.1.165","v6.1.164","v6.1.163"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