[PATCH 6.6.y 2/2] 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 comment/define changes for missing QRTR_NS_MAX_SERVERS/LOOKUPS prereqs and kept plain kzalloc instead of kzalloc_obj ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/qrtr/ns.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/net/qrtr/ns.c b/net/qrtr/ns.c
index 7f7bd87cc6052..8a545b66d14bb 100644
--- a/net/qrtr/ns.c
+++ b/net/qrtr/ns.c
@@ -69,6 +69,13 @@ struct qrtr_node {
 	struct xarray servers;
 };
 
+/* Max nodes limit is chosen based on the current platform requirements.
+ * If the requirement changes in the future, this value can be increased.
+ */
+#define QRTR_NS_MAX_NODES   64
+
+static u8 node_count;
+
 static struct qrtr_node *node_get(unsigned int node_id)
 {
 	struct qrtr_node *node;
@@ -77,6 +84,11 @@ 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)
@@ -90,6 +102,8 @@ static struct qrtr_node *node_get(unsigned int node_id)
 		return NULL;
 	}
 
+	node_count++;
+
 	return node;
 }
 
@@ -383,6 +397,7 @@ static int ctrl_cmd_bye(struct sockaddr_qrtr *from)
 delete_node:
 	xa_erase(&nodes, from->sq_node);
 	kfree(node);
+	node_count--;
 
 	return ret;
 }
-- 
2.53.0