[PATCH 5.15.y] net: qrtr: ns: Limit the total number of nodes

[Sasha Levin <sashal@kernel.org>]

From: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>

[ Upstream commit 27d5e84e810b0849d08b9aec68e48570461ce313 ]

Currently, the nameserver doesn't limit the number of nodes it handles.
This can be an attack vector if a malicious client starts registering
random nodes, leading to memory exhaustion.

Hence, limit the maximum number of nodes to 64. Note that, limit of 64 is
chosen based on the current platform requirements. If requirement changes
in the future, this limit can be increased.

Cc: stable@vger.kernel.org
Fixes: 0c2204a4ad71 ("net: qrtr: Migrate nameservice to kernel from userspace")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Link: https://patch.msgid.link/20260409-qrtr-fix-v3-4-00a8a5ff2b51@oss.qualcomm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ dropped node_count-- hunk since ctrl_cmd_bye() has no delete_node ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/qrtr/ns.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/net/qrtr/ns.c b/net/qrtr/ns.c
index 3c513e7ca2d5c..03b5ae3100de7 100644
--- a/net/qrtr/ns.c
+++ b/net/qrtr/ns.c
@@ -68,6 +68,16 @@ struct qrtr_node {
 	struct radix_tree_root servers;
 };
 
+/* Max nodes, server, lookup limits are chosen based on the current platform
+ * requirements. If the requirement changes in the future, these values can be
+ * increased.
+ */
+#define QRTR_NS_MAX_NODES   64
+#define QRTR_NS_MAX_SERVERS 256
+#define QRTR_NS_MAX_LOOKUPS 64
+
+static u8 node_count;
+
 static struct qrtr_node *node_get(unsigned int node_id)
 {
 	struct qrtr_node *node;
@@ -76,6 +86,11 @@ static struct qrtr_node *node_get(unsigned int node_id)
 	if (node)
 		return node;
 
+	if (node_count >= QRTR_NS_MAX_NODES) {
+		pr_err_ratelimited("QRTR clients exceed max node limit!\n");
+		return NULL;
+	}
+
 	/* If node didn't exist, allocate and insert it to the tree */
 	node = kzalloc(sizeof(*node), GFP_KERNEL);
 	if (!node)
@@ -88,6 +103,8 @@ static struct qrtr_node *node_get(unsigned int node_id)
 		return NULL;
 	}
 
+	node_count++;
+
 	return node;
 }
 
-- 
2.53.0