CVE-2025-37890

In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc As described in Gerrard's report [1], we have a UAF case when an hfsc class has a netem child qdisc. The crux of the issue is that hfsc is assuming that checking for cl->qdisc->q.qlen == 0 guarantees that it hasn't inserted the class in the vttree or eltree (which is not true for the netem duplicate case). This patch checks the n_active class variable to make sure that the code won't insert the class in the vttree or eltree twice, catering for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

• linux linux kernel (>= 5.0.1 < 5.4.294) • linux linux kernel (>= 5.5 < 5.10.238) • linux linux kernel (>= 5.11 < 5.15.182) • linux linux kernel (>= 5.16 < 6.1.138) • linux linux kernel (>= 6.2 < 6.6.90) • linux linux kernel (>= 6.7 < 6.12.28) • linux linux kernel (>= 6.13 < 6.14.6) • linux linux kernel 5.0 • linux linux kernel 6.15 • debian debian linux 11.0