linux-kernel - [PATCH v2] device property: fix of node refcount leak in fwnode_graph_get_next

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Date:   Tue, 22 Nov 2022 20:00:39 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <andriy.shevchenko@...ux.intel.com>, <djrscally@...il.com>,
        <heikki.krogerus@...ux.intel.com>, <sakari.ailus@...ux.intel.com>,
        <gregkh@...uxfoundation.org>, <rafael@...nel.org>
Subject: [PATCH v2] device property: fix of node refcount leak in fwnode_graph_get_next_endpoint()

The 'parent' returned by fwnode_graph_get_port_parent()
with refcount incremented when 'prev' is not null, it
needs be put when finish using it.

Because the parent is const, introduce a new variable to
store the returned fwnode, then put it before returning
from fwnode_graph_get_next_endpoint().

Fixes: b5b41ab6b0c1 ("device property: Check fwnode->secondary in fwnode_graph_get_next_endpoint()")
Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
---
v1 -> v2:
  Introduce a new variable to store the returned fwnode.
---
 drivers/base/property.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 2a5a37fcd998..7a32582aaca8 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -989,26 +989,32 @@ struct fwnode_handle *
 fwnode_graph_get_next_endpoint(const struct fwnode_handle *fwnode,
 			       struct fwnode_handle *prev)
 {
+	struct fwnode_handle *ep, *port_parent = NULL;
 	const struct fwnode_handle *parent;
-	struct fwnode_handle *ep;
 
 	/*
 	 * If this function is in a loop and the previous iteration returned
 	 * an endpoint from fwnode->secondary, then we need to use the secondary
 	 * as parent rather than @fwnode.
 	 */
-	if (prev)
-		parent = fwnode_graph_get_port_parent(prev);
-	else
+	if (prev) {
+		port_parent = fwnode_graph_get_port_parent(prev);
+		parent = port_parent;
+	} else {
 		parent = fwnode;
+	}
 	if (IS_ERR_OR_NULL(parent))
 		return NULL;
 
 	ep = fwnode_call_ptr_op(parent, graph_get_next_endpoint, prev);
-	if (ep)
+	if (ep) {
+		fwnode_handle_put(port_parent);
 		return ep;
+	}
 
-	return fwnode_graph_get_next_endpoint(parent->secondary, NULL);
+	ep = fwnode_graph_get_next_endpoint(parent->secondary, NULL);
+	fwnode_handle_put(port_parent);
+	return ep;
 }
 EXPORT_SYMBOL_GPL(fwnode_graph_get_next_endpoint);
 
-- 
2.25.1