net_sched: qfq: Fix double list add in class with netem as child qdisc

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In the Linux kernel, the following vulnerability has been resolved: net_sched: qfq: Fix double list add in class with netem as child qdisc As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of qfq, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. This patch checks whether the class was already added to the agg->active list (cl_is_active) before doing the addition to cater for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+[email protected]/

Source published

20 May 2025 15:21:44 UTC

Source modified

15 Oct 2026 21:52:02 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H