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authorYunjian Wang <wangyunjian@huawei.com>2021-06-04 14:03:18 +0300
committerDavid S. Miller <davem@davemloft.net>2021-06-05 00:44:18 +0300
commit944d671d5faa0d78980a3da5c0f04960ef1ad893 (patch)
tree61215bceb853496d1e709ad7a4ad2658878d51f6 /net
parent26821ecd3b489c11ecfbd3942bc7fef7629464b6 (diff)
downloadlinux-944d671d5faa0d78980a3da5c0f04960ef1ad893.tar.xz
sch_htb: fix refcount leak in htb_parent_to_leaf_offload
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@huawei.com> Suggested-by: Maxim Mikityanskiy <maximmi@nvidia.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/sched/sch_htb.c8
1 files 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);
}
}