net_shaper_nl_group_doit() does not deduplicate NET_SHAPER_A_LEAVES
entries. When userspace supplies the same leaf handle twice, the same
old-parent pointer lands twice in old_nodes[]. The cleanup loop double
frees the parent. Of course the same parent may still be in old_nodes[]
twice if we are moving multiple of its leaves.

Note that this patch also implicitly fixes the fact that the
i >= leaves_count path forgets to set ret.

Fixes: 5d5d4700e75d ("net-shapers: implement NL group operation")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/shaper/shaper.c | 60 +++++++++++++++++++++++++++++++++------------
 1 file changed, 45 insertions(+), 15 deletions(-)

diff --git a/net/shaper/shaper.c b/net/shaper/shaper.c
index a2e9adca9afc..a27673e5919f 100644
--- a/net/shaper/shaper.c
+++ b/net/shaper/shaper.c
@@ -955,6 +955,46 @@ static int net_shaper_handle_cmp(const struct net_shaper_handle *a,
 	return memcmp(a, b, sizeof(*a));
 }
 
+static int net_shaper_parse_leaves(struct net_shaper_binding *binding,
+				   struct genl_info *info,
+				   const struct net_shaper *node,
+				   struct net_shaper *leaves,
+				   int leaves_count)
+{
+	struct nlattr *attr;
+	int i, j, ret, rem;
+
+	i = 0;
+	nla_for_each_attr_type(attr, NET_SHAPER_A_LEAVES,
+			       genlmsg_data(info->genlhdr),
+			       genlmsg_len(info->genlhdr), rem) {
+		if (WARN_ON_ONCE(i >= leaves_count))
+			return -EINVAL;
+
+		ret = net_shaper_parse_leaf(binding, attr, info,
+					    node, &leaves[i]);
+		if (ret)
+			return ret;
+
+		/* Reject duplicates */
+		for (j = 0; j < i; j++) {
+			if (net_shaper_handle_cmp(&leaves[i].handle,
+						  &leaves[j].handle))
+				continue;
+
+			NL_SET_ERR_MSG_ATTR_FMT(info->extack, attr,
+						"Duplicate leaf shaper %d:%d",
+						leaves[i].handle.scope,
+						leaves[i].handle.id);
+			return -EINVAL;
+		}
+
+		i++;
+	}
+
+	return 0;
+}
+
 static int net_shaper_parent_from_leaves(int leaves_count,
 					 const struct net_shaper *leaves,
 					 struct net_shaper *node,
@@ -1195,10 +1235,9 @@ int net_shaper_nl_group_doit(struct sk_buff *skb, struct genl_info *info)
 	struct net_shaper **old_nodes, *leaves, node = {};
 	struct net_shaper_hierarchy *hierarchy;
 	struct net_shaper_binding *binding;
-	int i, ret, rem, leaves_count;
+	int i, ret, leaves_count;
 	int old_nodes_count = 0;
 	struct sk_buff *msg;
-	struct nlattr *attr;
 
 	if (GENL_REQ_ATTR_CHECK(info, NET_SHAPER_A_LEAVES))
 		return -EINVAL;
@@ -1226,19 +1265,10 @@ int net_shaper_nl_group_doit(struct sk_buff *skb, struct genl_info *info)
 	if (ret)
 		goto free_leaves;
 
-	i = 0;
-	nla_for_each_attr_type(attr, NET_SHAPER_A_LEAVES,
-			       genlmsg_data(info->genlhdr),
-			       genlmsg_len(info->genlhdr), rem) {
-		if (WARN_ON_ONCE(i >= leaves_count))
-			goto free_leaves;
-
-		ret = net_shaper_parse_leaf(binding, attr, info,
-					    &node, &leaves[i]);
-		if (ret)
-			goto free_leaves;
-		i++;
-	}
+	ret = net_shaper_parse_leaves(binding, info, &node,
+				      leaves, leaves_count);
+	if (ret)
+		goto free_leaves;
 
 	/* Prepare the msg reply in advance, to avoid device operation
 	 * rollback on allocation failure.
-- 
2.54.0