4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Pedro Tammela <pctammela@xxxxxxxxxxxx>
[ 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@xxxxxxxxx>
Suggested-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
Tested-by: Victor Nogueira <victor@xxxxxxxxxxxx>
Signed-off-by: Pedro Tammela <pctammela@xxxxxxxxxxxx>
Signed-off-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
net/sched/sch_api.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
Link: https://patch.msgid.link/20241024165547.418570-1-jhs@xxxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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)
--
2.43.0
