5.4-stable review patch. If anyone has any objections, please let me know.
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From: Victor Nogueira victor@mojatatu.com
[ Upstream commit 141d34391abbb315d68556b7c67ad97885407547 ]
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-...
Fixes: 37d9cf1a3ce3 ("sched: Fix detection of empty queues in child qdiscs") Reported-by: Gerrard Tai gerrard.tai@starlabs.sg Acked-by: Jamal Hadi Salim jhs@mojatatu.com Signed-off-by: Victor Nogueira victor@mojatatu.com Link: https://patch.msgid.link/20250425220710.3964791-3-victor@mojatatu.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/sch_hfsc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c index 79c63c4610d3a..5d73d02b8dce7 100644 --- a/net/sched/sch_hfsc.c +++ b/net/sched/sch_hfsc.c @@ -1573,7 +1573,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) return err; }
- if (first) { + if (first && !cl->cl_nactive) { if (cl->cl_flags & HFSC_RSC) init_ed(cl, len); if (cl->cl_flags & HFSC_FSC)