4.19-stable review patch. If anyone has any objections, please let me know.
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From: Pedro Tammela pctammela@mojatatu.com
[ Upstream commit 2e95c4384438adeaa772caa560244b1a2efef816 ]
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 markovicbudimir@gmail.com Suggested-by: Jamal Hadi Salim jhs@mojatatu.com Tested-by: Victor Nogueira victor@mojatatu.com Signed-off-by: Pedro Tammela pctammela@mojatatu.com Signed-off-by: Jamal Hadi Salim jhs@mojatatu.com
net/sched/sch_api.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Simon Horman horms@kernel.org
Link: https://patch.msgid.link/20241024165547.418570-1-jhs@mojatatu.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/sch_api.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index ab57c0ee9923b..49c4e85257886 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -783,7 +783,7 @@ void qdisc_tree_reduce_backlog(struct Qdisc *sch, unsigned int n, 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)