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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80630
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-28 08:16:47 UTC
Updated2026-08-29 07:16:47 UTC
DescriptionIn 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] <TASK> ... [ 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/

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.005210000 probability, percentile 0.421400000 (date 2026-08-31)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected cc71a757da78dd4aa1b4a9b19cb011833730ccf2 3e515188393e62a718ccebee651ee74514104ff6 git Not specified
CNA Linux Linux affected eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450 20dd591d8f951e1e6aca5052be8785e6181055e2 git Not specified
CNA Linux Linux affected 829c49b6b2ff45b043739168fd1245e4e1a91a30 94a5f1efdefb01f82cd228bf4e7ef1e8fc075c80 git Not specified
CNA Linux Linux affected 2f9761a94bae33d26e6a81b31b36e7d776d93dc1 acc08a0c7f37ebb1901144e03a7cba7d4afd9203 git Not specified
CNA Linux Linux affected 4d55144b12e742404bb3f8fee6038bafbf45619d 7c09843fd2b44d9bf0de798683861d1aecd62a08 git Not specified
CNA Linux Linux affected 342debc12183b51773b3345ba267e9263bdfaaef 0500af8630c3253f0dde879bd3a73a06bb2f2b3f git Not specified
CNA Linux Linux affected 342debc12183b51773b3345ba267e9263bdfaaef af54df2f44d9605614bc7ed96640302a240a9a62 git Not specified
CNA Linux Linux affected 342debc12183b51773b3345ba267e9263bdfaaef 097f6fc7b1ae362dd7a9444b2572162fda73b284 git Not specified
CNA Linux Linux affected 7a742a9506849d1c1aa71e36c89855ceddc7d58e git Not specified
CNA Linux Linux affected e73c838c80dccb9e4f19becc11d9f3cb4a27d483 git Not specified
CNA Linux Linux affected a57fe60ef4cf96bfbb6b58397ec28bdb5a5c6b31 git Not specified
CNA Linux Linux affected 5.10.241 5.10.261 semver Not specified
CNA Linux Linux affected 5.15.190 5.15.212 semver Not specified
CNA Linux Linux affected 6.1.135 6.1.178 semver Not specified
CNA Linux Linux affected 6.6.88 6.6.145 semver Not specified
CNA Linux Linux affected 6.12.24 6.12.97 semver Not specified
CNA Linux Linux affected 5.4.297 5.5 semver Not specified
CNA Linux Linux affected 6.13.12 6.14 semver Not specified
CNA Linux Linux affected 6.14.3 6.15 semver Not specified
CNA Linux Linux affected 6.15 Not specified
CNA Linux Linux unaffected 6.15 semver Not specified
CNA Linux Linux unaffected 5.10.261 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.212 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.178 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.145 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.97 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.40 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.5 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/acc08a0c7f37ebb1901144e03a7cba7d4afd9203 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/94a5f1efdefb01f82cd228bf4e7ef1e8fc075c80 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/097f6fc7b1ae362dd7a9444b2572162fda73b284 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/af54df2f44d9605614bc7ed96640302a240a9a62 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/20dd591d8f951e1e6aca5052be8785e6181055e2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7c09843fd2b44d9bf0de798683861d1aecd62a08 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0500af8630c3253f0dde879bd3a73a06bb2f2b3f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3e515188393e62a718ccebee651ee74514104ff6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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