UPSTREAM: net: sched: Disallow replacing of child qdisc from one parent to another am: 4fd7634f

Original change: https://android-review.googlesource.com/c/kernel/common/+/3548021



Change-Id: Ic0edee0e263cec0d194a74e69fef36f8348eea86
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

net/sched/sch_api.c

@@ -1603,6 +1603,10 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 				q = qdisc_lookup(dev, tcm->tcm_handle);
 				if (!q)
 					goto create_n_graft;
+				if (q->parent != tcm->tcm_parent) {
+					NL_SET_ERR_MSG(extack, "Cannot move an existing qdisc to a different parent");
+					return -EINVAL;
+				}
 				if (n->nlmsg_flags & NLM_F_EXCL) {
 					NL_SET_ERR_MSG(extack, "Exclusivity flag on, cannot override");
 					return -EEXIST;