[PATCH v10 07/10] PCI: of: Clear fwnode->dev during root bridge node removal and error path

[Herve Codina <herve.codina@bootlin.com>]

During the of_pci_make_host_bridge_node() call, an OF node is created
dynamically and its fwnode device (fwnode->dev) is set to the PCI root
bridge device using the fw_devlink_set_device(&np->fwnode, &bridge->dev)
call.

On removal, of_pci_remove_host_bridge_node() is called and calls
device_remove_of_node() which in turn set to NULL the related
dev->fwnode.

Later in the removal sequence, device_del() is called and runs its
cleanup logic:

    if (dev->fwnode && dev->fwnode->dev == dev)
        fw_devlink_set_device(dev->fwnode, NULL);

Because dev->fwnode has been cleared earlier, fw_devlink_set_device()
is not called and leaves fwnode->dev unchanged. This fwnode device
(fwnode->dev) becomes an dangling pointer.

If any reference to the OF node is held after this removal, the pointer
is still accessible using the OF node (np->fwnode.dev) but points to a
freed area.

The exact same issue is present in the of_pci_make_host_bridge_node()
error path leading to the exact same dangling fwnode->dev.

Avoid this dangling fwnode->dev pointer by clearing it in
of_pci_remove_host_bridge_node() and in of_pci_make_host_bridge_node()
error path.

Fixes: 1f340724419e ("PCI: of: Create device tree PCI host bridge node")
Cc: stable@vger.kernel.org
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/pci/of.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index ee9eb384b377..6a533f9bbf3c 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -743,6 +743,7 @@ void of_pci_remove_host_bridge_node(struct pci_host_bridge *bridge)
 	if (!np || !of_node_check_flag(np, OF_DYNAMIC))
 		return;
 
+	fw_devlink_set_device(&np->fwnode, NULL);
 	device_remove_of_node(&bridge->bus->dev);
 	device_remove_of_node(&bridge->dev);
 	of_changeset_revert(np->data);
@@ -808,7 +809,7 @@ void of_pci_make_host_bridge_node(struct pci_host_bridge *bridge)
 
 	ret = of_changeset_apply(cset);
 	if (ret)
-		goto out_free_node;
+		goto out_clear_devlink_dev;
 
 	np->data = cset;
 
@@ -830,6 +831,8 @@ void of_pci_make_host_bridge_node(struct pci_host_bridge *bridge)
 out_revert_cset:
 	np->data = NULL;
 	of_changeset_revert(cset);
+out_clear_devlink_dev:
+	fw_devlink_set_device(&np->fwnode, NULL);
 out_free_node:
 	of_node_put(np);
 out_destroy_cset:
-- 
2.55.0