Bug 2502893 (CVE-2026-64207)

Summary: CVE-2026-64207 kernel: net/sched: dualpi2: fix GSO backlog accounting
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's DualPI2 (Dual-rate PI2) queue discipline. This vulnerability arises from incorrect accounting of Generic Segmentation Offload (GSO) backlog, where the parent queue (such as QFQ - Hierarchical Fair Queueing) miscalculates the number of queued packets. This miscalculation can lead to a NULL pointer dereference when the system attempts to dequeue packets from an inactive class, resulting in a system crash and a Denial of Service (DoS) condition.
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Description OSIDB Bzimport 2026-07-20 17:04:19 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net/sched: dualpi2: fix GSO backlog accounting

When DualPI2 splits a GSO skb into N segments, it propagates N
additional packets to its parent before returning NET_XMIT_SUCCESS.
The parent then accounts for the original skb once more, leaving its
qlen one larger than the number of packets actually queued.

With QFQ as the parent, after all real packets are dequeued, QFQ still
has a non-zero qlen while its in-service aggregate has no active
classes. qfq_choose_next_agg() returns NULL and qfq_dequeue() passes
the result to qfq_peek_skb(), causing a NULL pointer dereference.

Follow the same pattern used by tbf_segment() and taprio: count only
successfully queued segments, propagate the difference between the
original skb and those segments, and return NET_XMIT_SUCCESS whenever
at least one segment was queued.
Comment 1 TEJ RATHI 2026-07-21 03:57:20 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072053-CVE-2026-64207-e76b@gregkh/T