[PATCH 5.15.y] net: qrtr: ns: Limit the maximum server registration per node

From: Manivannan Sadhasivam <[email protected]>

Current code does no bound checking on the number of servers added per
node. A malicious client can flood NEW_SERVER messages and exhaust memory.

Fix this issue by limiting the maximum number of server registrations to
256 per node. If the NEW_SERVER message is received for an old port, then
don't restrict it as it will get replaced. While at it, also rate limit
the error messages in the failure path of qrtr_ns_worker().

Note that the limit of 256 is chosen based on the current platform
requirements. If requirement changes in the future, this limit can be
increased.

Cc: [email protected]
Fixes: 0c2204a4ad71 ("net: qrtr: Migrate nameservice to kernel from userspace")
Reported-by: Yiming Qian <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: Manivannan Sadhasivam <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
(cherry picked from commit d5ee2ff98322337951c56398e79d51815acbf955)
Signed-off-by: Youssef Samir <[email protected]>
---
 net/qrtr/ns.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/net/qrtr/ns.c b/net/qrtr/ns.c
index 559aad0e3621..91e43b0fd566 100644
--- a/net/qrtr/ns.c
+++ b/net/qrtr/ns.c
@@ -68,13 +68,9 @@ struct qrtr_server {
 struct qrtr_node {
 	unsigned int id;
 	struct xarray servers;
+	u32 server_count;
 };
 
-/* Max lookup 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_LOOKUPS 64
-
 /* 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.
@@ -249,6 +245,17 @@ static struct qrtr_server *server_add(unsigned int service,
 	if (!service || !port)
 		return NULL;
 
+	node = node_get(node_id);
+	if (!node)
+		return NULL;
+
+	/* Make sure the new servers per port are capped at the maximum value */
+	old = xa_load(&node->servers, port);
+	if (!old && node->server_count >= QRTR_NS_MAX_SERVERS) {
+		pr_err_ratelimited("QRTR client node %u exceeds max server limit!\n", node_id);
+		return NULL;
+	}
+
 	srv = kzalloc(sizeof(*srv), GFP_KERNEL);
 	if (!srv)
 		return NULL;
@@ -258,10 +265,6 @@ static struct qrtr_server *server_add(unsigned int service,
 	srv->node = node_id;
 	srv->port = port;
 
-	node = node_get(node_id);
-	if (!node)
-		goto err;
-
 	/* Delete the old server on the same port */
 	old = xa_store(&node->servers, port, srv, GFP_KERNEL);
 	if (old) {
@@ -272,6 +275,8 @@ static struct qrtr_server *server_add(unsigned int service,
 		} else {
 			kfree(old);
 		}
+	} else {
+		node->server_count++;
 	}
 
 	trace_qrtr_ns_server_add(srv->service, srv->instance,
@@ -312,6 +317,7 @@ static int server_del(struct qrtr_node *node, unsigned int port, bool bcast)
 	}
 
 	kfree(srv);
+	node->server_count--;
 
 	return 0;
 }
@@ -708,7 +714,7 @@ static void qrtr_ns_worker(struct work_struct *work)
 		}
 
 		if (ret < 0)
-			pr_err("failed while handling packet from %d:%d",
+			pr_err_ratelimited("failed while handling packet from %d:%d",
 			       sq.sq_node, sq.sq_port);
 	}
 
-- 
2.43.0