net/sched: sch_dualpi2: drain both C-queue and L-queue in dualpi2_change()

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Summary

CVECVE-2026-52997
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-24 17:17:10 UTC
Updated2026-06-24 17:17:10 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net/sched: sch_dualpi2: drain both C-queue and L-queue in dualpi2_change() Fix dualpi2_change() to correctly enforce updated limit and memlimit values after a configuration change of the dualpi2 qdisc. Before this patch, dualpi2_change() always attempted to dequeue packets via the root qdisc (C-queue) when reducing backlog or memory usage, and unconditionally assumed that a valid skb will be returned. When traffic classification results in packets being queued in the L-queue while the C-queue is empty, this leads to a NULL skb dereference during limit or memlimit enforcement. This is fixed by first dequeuing from the C-queue path if it is non-empty. Once the C-queue is empty, packets are dequeued directly from the L-queue. Return values from qdisc_dequeue_internal() are checked for both queues. When dequeuing from the L-queue, the parent qdisc qlen and backlog counters are updated explicitly to keep overall qdisc statistics consistent.

Risk And Classification

EPSS: 0.001730000 probability, percentile 0.069770000 (date 2026-06-25)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 320d031ad6e4d67e8e1ab08ac71efda02bc85683 86cf2eba2056bcf9c41fba260e599bd95bf9943b git Not specified
CNA Linux Linux affected 320d031ad6e4d67e8e1ab08ac71efda02bc85683 3042add80c2c50bd127d570b83319af612efde65 git Not specified
CNA Linux Linux affected 320d031ad6e4d67e8e1ab08ac71efda02bc85683 478ed6b7d2577439c610f91fa8759a4c878a4264 git Not specified
CNA Linux Linux affected 6.17 Not specified
CNA Linux Linux unaffected 6.17 semver Not specified
CNA Linux Linux unaffected 6.18.33 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.10 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/86cf2eba2056bcf9c41fba260e599bd95bf9943b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3042add80c2c50bd127d570b83319af612efde65 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/478ed6b7d2577439c610f91fa8759a4c878a4264 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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