Re: v5.13-rcX regression - NULL pointer dereference - MFD and software node API

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

[-- Attachment #1: Type: text/plain, Size: 937 bytes --]

On Mon, Jun 21, 2021 at 01:00:06PM +0300, Andy Shevchenko wrote:
> Can you, please, attach this to the bug report?
> 
> Long story here is that the device creation fails but we already have added
> swnode to it. Meanwhile, device itself is not completely instantiated (yet)
> and dev_name(dev) is NULL. The software_node_notify() is called with such
> device and Oopses in the following line
> 
> 	sysfs_remove_link(&swnode->kobj, dev_name(dev));
> 
> My patch fixes another issue that might happen before this and in the code
> that retrieves swnode itself in the device_remove_software_node().
> 
> Of course my patch won't fix this issue.
> 
> I have heard that Heikki is looking how to fix the issue in your case and
> potentially in any other cases where device_add_software_node() is called
> against not formed object instance.

Dominik, can you test the attached patch to confirm if this really is
the case.

thanks,

-- 
heikki

[-- Attachment #2: 0001-software-node-Handle-software-node-injection-to-an-e.patch --]
[-- Type: text/plain, Size: 1759 bytes --]

From 0cddd29f5d5d41d1b7fa38b0f927f4e755a1bcd0 Mon Sep 17 00:00:00 2001
From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Date: Mon, 21 Jun 2021 13:31:51 +0300
Subject: [PATCH] software node: Handle software node injection to an existing
 device properly

Interim, work-in-progress.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
 drivers/base/swnode.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 3cc11b813f28c..33c8f31dbab4f 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -1045,7 +1045,15 @@ int device_add_software_node(struct device *dev, const struct software_node *nod
 	}
 
 	set_secondary_fwnode(dev, &swnode->fwnode);
-	software_node_notify(dev, KOBJ_ADD);
+
+	/*
+	 * In some special cases the software node has to be injected to an
+	 * already existing device. In these cases software_node_node() has to
+	 * be called separate from here. Using the device name here to check was
+	 * the device already added or not.
+	 */
+	if (dev_name(dev))
+		software_node_notify(dev, KOBJ_ADD);
 
 	return 0;
 }
@@ -1065,7 +1073,8 @@ void device_remove_software_node(struct device *dev)
 	if (!swnode)
 		return;
 
-	software_node_notify(dev, KOBJ_REMOVE);
+	if (dev_name(dev))
+		software_node_notify(dev, KOBJ_REMOVE);
 	set_secondary_fwnode(dev, NULL);
 	kobject_put(&swnode->kobj);
 }
@@ -1119,8 +1128,7 @@ int software_node_notify(struct device *dev, unsigned long action)
 
 	switch (action) {
 	case KOBJ_ADD:
-		ret = sysfs_create_link_nowarn(&dev->kobj, &swnode->kobj,
-					       "software_node");
+		ret = sysfs_create_link(&dev->kobj, &swnode->kobj, "software_node");
 		if (ret)
 			break;
 
-- 
2.30.2