{"id":"CVE-2026-80630","summary":"net/sched: sch_fq_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_fq_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen\n\nWhenever fq_codel drops packets during peek, it calls\nqdisc_tree_reduce_backlog. An issue arises because it calls\nqdisc_tree_reduce_backlog before it reincrements the qlen. If qlen drops\nto zero, but peek returns an skb, the parent's qlen_notify callback will be\nexecuted even though fq_codel still has 1 packet on the queue and, thus,\nwill mistakenly deactivate the parent's class causing issues like a recent\nreport [1] and a wild memory access in qfq:\n\n[   29.371146][  T360] Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI\n[   29.371666][  T360] KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127]\n[   29.371987][  T360] CPU: 6 UID: 0 PID: 360 Comm: tc Not tainted 7.1.0-rc5-00285-gc530e5b2dbc6-dirty #82 PREEMPT(full)\n[   29.372384][  T360] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011\n[   29.372620][  T360] RIP: 0010:qfq_deactivate_agg (include/linux/list.h:1029 (discriminator 2) include/linux/list.h:1043 (discriminator 2) net/sched/sch_qfq.c:1369 (discriminator 2) net/sched/sch_qfq.c:1395 (discriminator 2)) sch_qfq\n[   29.373544][  T360] RSP: 0018:ffff888102417370 EFLAGS: 00010216\n[   29.373800][  T360] RAX: 0000000000000000 RBX: ffff88811224d568 RCX: dffffc0000000000\n[   29.374079][  T360] RDX: 1ffff11021fe1543 RSI: ffff88810ff0aa00 RDI: dffffc0000000000\n[   29.374368][  T360] RBP: ffff88811224c280 R08: dead000000000122 R09: 1bd5a00000000024\n[   29.374649][  T360] R10: fffffbfff7940329 R11: fffffbfff7940329 R12: 0000000000000000\n[   29.374926][  T360] R13: dead000000000100 R14: ffff88811224d580 R15: ffff88811224d578\n[   29.375207][  T360] FS:  00007f5b794e5780(0000) GS:ffff88815d1e9000(0000) knlGS:0000000000000000\n[   29.375545][  T360] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   29.375823][  T360] CR2: 000055ffb091f000 CR3: 000000010a305000 CR4: 0000000000750ef0\n[   29.376103][  T360] PKRU: 55555554\n[   29.376258][  T360] Call Trace:\n[   29.376401][  T360]  \u003cTASK\u003e\n...\n[   29.376885][  T360] qfq_reset_qdisc (net/sched/sch_qfq.c:357 net/sched/sch_qfq.c:1487) sch_qfq\n[   29.377074][  T360]  qdisc_reset (net/sched/sch_generic.c:1057)\n[   29.377414][  T360]  __qdisc_destroy (net/sched/sch_generic.c:1096)\n[   29.377600][  T360]  qdisc_graft (net/sched/sch_api.c:1062 net/sched/sch_api.c:1053 net/sched/sch_api.c:1159)\n[   29.378593][  T360]  tc_get_qdisc (net/sched/sch_api.c:1528 net/sched/sch_api.c:1556)\n\nFix this by only calling qdisc_tree_reduce_backlog in peek after the\nqlen is restored.\n\n[1] http://lore.kernel.org/netdev/CAN2cbVe79oj0O9==m4+4x3v+O+qzRagA=2=wkrp9i9=CqYvyZA@mail.gmail.com/","modified":"2026-10-28T02:30:24.557764418Z","published":"2026-08-28T06:48:46.569Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80630.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0500af8630c3253f0dde879bd3a73a06bb2f2b3f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/097f6fc7b1ae362dd7a9444b2572162fda73b284"},{"type":"WEB","url":"https://git.kernel.org/stable/c/20dd591d8f951e1e6aca5052be8785e6181055e2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3e515188393e62a718ccebee651ee74514104ff6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7c09843fd2b44d9bf0de798683861d1aecd62a08"},{"type":"WEB","url":"https://git.kernel.org/stable/c/94a5f1efdefb01f82cd228bf4e7ef1e8fc075c80"},{"type":"WEB","url":"https://git.kernel.org/stable/c/acc08a0c7f37ebb1901144e03a7cba7d4afd9203"},{"type":"WEB","url":"https://git.kernel.org/stable/c/af54df2f44d9605614bc7ed96640302a240a9a62"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80630.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80630"},{"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":"cc71a757da78dd4aa1b4a9b19cb011833730ccf2"},{"fixed":"3e515188393e62a718ccebee651ee74514104ff6"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450"},{"fixed":"20dd591d8f951e1e6aca5052be8785e6181055e2"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"829c49b6b2ff45b043739168fd1245e4e1a91a30"},{"fixed":"94a5f1efdefb01f82cd228bf4e7ef1e8fc075c80"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"2f9761a94bae33d26e6a81b31b36e7d776d93dc1"},{"fixed":"acc08a0c7f37ebb1901144e03a7cba7d4afd9203"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4d55144b12e742404bb3f8fee6038bafbf45619d"},{"fixed":"7c09843fd2b44d9bf0de798683861d1aecd62a08"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"342debc12183b51773b3345ba267e9263bdfaaef"},{"fixed":"0500af8630c3253f0dde879bd3a73a06bb2f2b3f"},{"fixed":"af54df2f44d9605614bc7ed96640302a240a9a62"},{"fixed":"097f6fc7b1ae362dd7a9444b2572162fda73b284"}]},{"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":"6.1.135"},{"fixed":"6.1.178"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.6.88"},{"fixed":"6.6.145"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.12.24"},{"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":"6.13.12"},{"fixed":"6.14"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.14.3"},{"fixed":"6.15"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"7a742a9506849d1c1aa71e36c89855ceddc7d58e"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"e73c838c80dccb9e4f19becc11d9f3cb4a27d483"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"a57fe60ef4cf96bfbb6b58397ec28bdb5a5c6b31"}]}],"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.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