Linux Kernel DualPI2 GSO backlog bug causing QFQ NULL pointer
CVE-2026-64207 Published on July 20, 2026
net/sched: dualpi2: fix GSO backlog accounting
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.
Products Associated with CVE-2026-64207
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Affected Versions
Linux:- Version 8f9516daedd67097a0c6e463fcb7a42b5ee9d477 and below c4b70c1512b8f9f33f23c2c8196dfd1210207681 is affected.
- Version 8f9516daedd67097a0c6e463fcb7a42b5ee9d477 and below 806586e33891066487db1f002be3d455cda6b516 is affected.
- Version 8f9516daedd67097a0c6e463fcb7a42b5ee9d477 and below 05ed733b65ab977dd931e7f7ac0f62fdb81205c2 is affected.
- Version 6.17 is affected.
- Before 6.17 is unaffected.
- Version 6.18.39, <= 6.18.* is unaffected.
- Version 7.1.4, <= 7.1.* is unaffected.
- Version 7.2-rc1, <= * is unaffected.