From: Yunjian Wang <wangyunjian@xxxxxxxxxx>
[ Upstream commit 944d671d5faa0d78980a3da5c0f04960ef1ad893 ]
The commit ae81feb7338c ("sch_htb: fix null pointer dereference
on a null new_q") fixes a NULL pointer dereference bug, but it
is not correct.
Because htb_graft_helper properly handles the case when new_q
is NULL, and after the previous patch by skipping this call
which creates an inconsistency : dev_queue->qdisc will still
point to the old qdisc, but cl->parent->leaf.q will point to
the new one (which will be noop_qdisc, because new_q was NULL).
The code is based on an assumption that these two pointers are
the same, so it can lead to refcount leaks.
The correct fix is to add a NULL pointer check to protect
qdisc_refcount_inc inside htb_parent_to_leaf_offload.
Fixes: ae81feb7338c ("sch_htb: fix null pointer dereference on a null new_q")
Signed-off-by: Yunjian Wang <wangyunjian@xxxxxxxxxx>
Suggested-by: Maxim Mikityanskiy <maximmi@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/sched/sch_htb.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 081c11d5717c..8827987ba903 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1488,7 +1488,8 @@ static void htb_parent_to_leaf_offload(struct Qdisc *sch,
struct Qdisc *old_q;
/* One ref for cl->leaf.q, the other for dev_queue->qdisc. */
- qdisc_refcount_inc(new_q);
+ if (new_q)
+ qdisc_refcount_inc(new_q);
old_q = htb_graft_helper(dev_queue, new_q);
WARN_ON(!(old_q->flags & TCQ_F_BUILTIN));
}
@@ -1675,10 +1676,9 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg,
cl->parent->common.classid,
NULL);
if (q->offload) {
- if (new_q) {
+ if (new_q)
htb_set_lockdep_class_child(new_q);
- htb_parent_to_leaf_offload(sch, dev_queue, new_q);
- }
+ htb_parent_to_leaf_offload(sch, dev_queue, new_q);
}
}
--
2.30.2
