GHSA-X458-6J5F-W8XQ

Vulnerability from github – Published: 2026-08-28 09:31 – Updated: 2026-08-29 09:30
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

net/sched: sch_fq_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen

Whenever fq_codel drops packets during peek, it calls qdisc_tree_reduce_backlog. An issue arises because it calls qdisc_tree_reduce_backlog before it reincrements the qlen. If qlen drops to zero, but peek returns an skb, the parent's qlen_notify callback will be executed even though fq_codel still has 1 packet on the queue and, thus, will mistakenly deactivate the parent's class causing issues like a recent report [1] and a wild memory access in qfq:

[ 29.371146][ T360] Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI [ 29.371666][ T360] KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127] [ 29.371987][ T360] CPU: 6 UID: 0 PID: 360 Comm: tc Not tainted 7.1.0-rc5-00285-gc530e5b2dbc6-dirty #82 PREEMPT(full) [ 29.372384][ T360] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 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 [ 29.373544][ T360] RSP: 0018:ffff888102417370 EFLAGS: 00010216 [ 29.373800][ T360] RAX: 0000000000000000 RBX: ffff88811224d568 RCX: dffffc0000000000 [ 29.374079][ T360] RDX: 1ffff11021fe1543 RSI: ffff88810ff0aa00 RDI: dffffc0000000000 [ 29.374368][ T360] RBP: ffff88811224c280 R08: dead000000000122 R09: 1bd5a00000000024 [ 29.374649][ T360] R10: fffffbfff7940329 R11: fffffbfff7940329 R12: 0000000000000000 [ 29.374926][ T360] R13: dead000000000100 R14: ffff88811224d580 R15: ffff88811224d578 [ 29.375207][ T360] FS: 00007f5b794e5780(0000) GS:ffff88815d1e9000(0000) knlGS:0000000000000000 [ 29.375545][ T360] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 29.375823][ T360] CR2: 000055ffb091f000 CR3: 000000010a305000 CR4: 0000000000750ef0 [ 29.376103][ T360] PKRU: 55555554 [ 29.376258][ T360] Call Trace: [ 29.376401][ T360] ... [ 29.376885][ T360] qfq_reset_qdisc (net/sched/sch_qfq.c:357 net/sched/sch_qfq.c:1487) sch_qfq [ 29.377074][ T360] qdisc_reset (net/sched/sch_generic.c:1057) [ 29.377414][ T360] __qdisc_destroy (net/sched/sch_generic.c:1096) [ 29.377600][ T360] qdisc_graft (net/sched/sch_api.c:1062 net/sched/sch_api.c:1053 net/sched/sch_api.c:1159) [ 29.378593][ T360] tc_get_qdisc (net/sched/sch_api.c:1528 net/sched/sch_api.c:1556)

Fix this by only calling qdisc_tree_reduce_backlog in peek after the qlen is restored.

[1] http://lore.kernel.org/netdev/CAN2cbVe79oj0O9==m4+4x3v+O+qzRagA=2=wkrp9i9=CqYvyZA@mail.gmail.com/

Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2026-80630"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-28T08:16:47Z",
    "severity": "CRITICAL"
  },
  "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\u0027s qlen_notify callback will be\nexecuted even though fq_codel still has 1 packet on the queue and, thus,\nwill mistakenly deactivate the parent\u0027s 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/",
  "id": "GHSA-x458-6j5f-w8xq",
  "modified": "2026-08-29T09:30:26Z",
  "published": "2026-08-28T09:31:47Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80630"
    },
    {
      "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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