CVE-2026-72036net/sched: sch_multiq: Replace direct dequeue call with peek and qdisc_dequeue_peeked

Official description

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_multiq: Replace direct dequeue call with peek and qdisc_dequeue_peeked multiq_dequeue() takes a packet from a band's child with a direct ->dequeue() call after multiq_peek() peeked it. When the child is non-work-conserving the peek stashes the skb in the child's gso_skb, so the direct dequeue returns a different skb and orphans the stash, desyncing the child's qlen/backlog. With a qfq child reached through a peeking parent (e.g. tbf) this re-enters the child on an emptied list and dereferences NULL, panicking the kernel from softirq on ordinary egress. Take the packet through qdisc_dequeue_peeked(), as sch_prio already does and as sch_red and sch_sfb were just fixed to do. The helper is a no-op when the child has no stash, so a work-conserving child is unaffected.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/3e5fd9d14f2d228e7260251f2e4a1d41ba8f705a
• https://git.kernel.org/stable/c/eb1a9637f0bd84b5db8803af65dfb1f44785406f
• https://git.kernel.org/stable/c/7a5a1582710981ef6637de9f074a60a5b1d63222
• https://git.kernel.org/stable/c/86a61e46a1919e8abf4d227c204773dabb24068a
• https://git.kernel.org/stable/c/1b9cc255e8089606b92b2adf504e334573682821
• https://git.kernel.org/stable/c/5889064919a1e5c0a9469c54895000414fc46944
• https://git.kernel.org/stable/c/fffeb2ab5eeb823d4c2330571a098f63237c9049
• https://git.kernel.org/stable/c/54f6b0c843e228d499eb4b6bbb89df68cad9ad5d