[PATCH v3 4/5] net: qrtr: ns: Limit the total number of nodes

[Manivannan Sadhasivam via B4 Relay <devnull+manivannan.sadhasivam.oss.qualcomm.com@kernel.org>]

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

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>
---
 net/qrtr/ns.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/net/qrtr/ns.c b/net/qrtr/ns.c
index 1b9a90240a68..c0418764470b 100644
--- a/net/qrtr/ns.c
+++ b/net/qrtr/ns.c
@@ -71,12 +71,16 @@ struct qrtr_node {
 	u32 server_count;
 };
 
-/* Max server, lookup limits are chosen based on the current platform requirements.
- * If the requirement changes in the future, these values can be increased.
+/* 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;
@@ -85,6 +89,11 @@ 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_obj(*node);
 	if (!node)
@@ -98,6 +107,8 @@ static struct qrtr_node *node_get(unsigned int node_id)
 		return NULL;
 	}
 
+	node_count++;
+
 	return node;
 }
 
@@ -404,6 +415,7 @@ static int ctrl_cmd_bye(struct sockaddr_qrtr *from)
 delete_node:
 	xa_erase(&nodes, from->sq_node);
 	kfree(node);
+	node_count--;
 
 	return ret;
 }

-- 
2.51.0