From: Pedro Tammela Date: Thu, 24 Oct 2024 16:55:47 +0000 (-0400) Subject: net/sched: stop qdisc_tree_reduce_backlog on TC_H_ROOT X-Git-Tag: v6.12~100^2~11 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=2e95c4384438adeaa772caa560244b1a2efef816;p=platform%2Fkernel%2Flinux-amlogic.git net/sched: stop qdisc_tree_reduce_backlog on TC_H_ROOT In qdisc_tree_reduce_backlog, Qdiscs with major handle ffff: are assumed to be either root or ingress. This assumption is bogus since it's valid to create egress qdiscs with major handle ffff: Budimir Markovic found that for qdiscs like DRR that maintain an active class list, it will cause a UAF with a dangling class pointer. In 066a3b5b2346, the concern was to avoid iterating over the ingress qdisc since its parent is itself. The proper fix is to stop when parent TC_H_ROOT is reached because the only way to retrieve ingress is when a hierarchy which does not contain a ffff: major handle call into qdisc_lookup with TC_H_MAJ(TC_H_ROOT). In the scenario where major ffff: is an egress qdisc in any of the tree levels, the updates will also propagate to TC_H_ROOT, which then the iteration must stop. Fixes: 066a3b5b2346 ("[NET_SCHED] sch_api: fix qdisc_tree_decrease_qlen() loop") Reported-by: Budimir Markovic Suggested-by: Jamal Hadi Salim Tested-by: Victor Nogueira Signed-off-by: Pedro Tammela Signed-off-by: Jamal Hadi Salim net/sched/sch_api.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Simon Horman Link: https://patch.msgid.link/20241024165547.418570-1-jhs@mojatatu.com Signed-off-by: Jakub Kicinski --- diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index 2eefa4783879..a1d27bc039a3 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -791,7 +791,7 @@ void qdisc_tree_reduce_backlog(struct Qdisc *sch, int n, int len) drops = max_t(int, n, 0); rcu_read_lock(); while ((parentid = sch->parent)) { - if (TC_H_MAJ(parentid) == TC_H_MAJ(TC_H_INGRESS)) + if (parentid == TC_H_ROOT) break; if (sch->flags & TCQ_F_NOPARENT)