[PATCH v11 10/10] PCI: of: Avoid np->data usage for the node changeset

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

of_pci_remove_node() and of_pci_remove_host_bridge_node() check
whether the node is dynamic but not whether it has valid private data.

During the node creation, an OF changeset is used and this changeset is
stored in np->data to be available for removal functions.

If, for instance, a PCI host bridge is created using a device-tree
overlay, the related node will have the dynamic flag set but np->data
will be NULL. This leads to NULL pointer dereferences.

Checking for a non-NULL np->data pointer to determine if the node has
been created by the PCI node creation process is not enough. Indeed,
on some platforms like PowerPC, the OF_RECONFIG_ATTACH_NODE notifier
(e.g., in the pci_dn_reconfig_notifier() function) intercepts node
additions and populates np->data with its own structure, such as a
struct pci_dn. In that case, np->data is not NULL but it is not related
to our changeset stored during the PCI node process creation.

Avoid the usage of np->data to store the changeset used during the PCI
node creation. Store our changeset in a more relevant structure: either
struct pci_dev when the node is created for a PCI device or struct
pci_host_bridge when the node is created for the PCI host bridge.

With that done, no ambiguity remains on removal. Indeed, this changeset,
if non-NULL, is the one used during PCI node creation. Check and use
this changeset on the removal process.

Fixes: 407d1a51921e ("PCI: Create device tree node for bridge")
Fixes: 1f340724419e ("PCI: of: Create device tree PCI host bridge node")
Cc: <stable+noautosel@kernel.org> # Issue not triggered but could be a problem
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/pci/of.c    | 28 ++++++++++++++--------------
 include/linux/pci.h | 11 +++++++++++
 2 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 0a5797652e18..cd87128c71dd 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -732,15 +732,16 @@ void of_pci_remove_node(struct pci_dev *pdev)
 {
 	struct device_node *np;
 
-	np = pci_device_to_OF_node(pdev);
-	if (!np || !of_node_check_flag(np, OF_DYNAMIC))
+	if (!pdev->cset)
 		return;
 
+	np = pci_device_to_OF_node(pdev);
 	fw_devlink_set_device(&np->fwnode, NULL);
 	device_remove_of_node(&pdev->dev);
-	of_changeset_revert(np->data);
-	of_changeset_destroy(np->data);
+	of_changeset_revert(pdev->cset);
+	of_changeset_destroy(pdev->cset);
 	of_node_put(np);
+	kfree(pdev->cset);
 }
 
 void of_pci_make_dev_node(struct pci_dev *pdev)
@@ -800,18 +801,17 @@ void of_pci_make_dev_node(struct pci_dev *pdev)
 	if (ret)
 		goto out_clear_devlink_dev;
 
-	np->data = cset;
-
 	ret = device_add_of_node(&pdev->dev, np);
 	if (ret)
 		goto out_revert_cset;
 
+	pdev->cset = cset;
+
 	kfree(name);
 
 	return;
 
 out_revert_cset:
-	np->data = NULL;
 	of_changeset_revert(cset);
 out_clear_devlink_dev:
 	fw_devlink_set_device(&np->fwnode, NULL);
@@ -828,16 +828,17 @@ void of_pci_remove_host_bridge_node(struct pci_host_bridge *bridge)
 {
 	struct device_node *np;
 
-	np = pci_bus_to_OF_node(bridge->bus);
-	if (!np || !of_node_check_flag(np, OF_DYNAMIC))
+	if (!bridge->cset)
 		return;
 
+	np = pci_bus_to_OF_node(bridge->bus);
 	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);
-	of_changeset_destroy(np->data);
+	of_changeset_revert(bridge->cset);
+	of_changeset_destroy(bridge->cset);
 	of_node_put(np);
+	kfree(bridge->cset);
 }
 
 void of_pci_make_host_bridge_node(struct pci_host_bridge *bridge)
@@ -899,8 +900,6 @@ void of_pci_make_host_bridge_node(struct pci_host_bridge *bridge)
 	if (ret)
 		goto out_clear_devlink_dev;
 
-	np->data = cset;
-
 	/* Add the of_node to host bridge and the root bus */
 	ret = device_add_of_node(&bridge->dev, np);
 	if (ret)
@@ -910,6 +909,8 @@ void of_pci_make_host_bridge_node(struct pci_host_bridge *bridge)
 	if (ret)
 		goto out_remove_bridge_dev_of_node;
 
+	bridge->cset = cset;
+
 	kfree(name);
 
 	return;
@@ -917,7 +918,6 @@ void of_pci_make_host_bridge_node(struct pci_host_bridge *bridge)
 out_remove_bridge_dev_of_node:
 	device_remove_of_node(&bridge->dev);
 out_revert_cset:
-	np->data = NULL;
 	of_changeset_revert(cset);
 out_clear_devlink_dev:
 	fw_devlink_set_device(&np->fwnode, NULL);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index d31a8d107b1e..7b0ba9ec7b5c 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -339,6 +339,9 @@ struct pcie_link_state;
 struct pci_sriov;
 struct pci_p2pdma;
 struct rcec_ea;
+#ifdef CONFIG_PCI_DYNAMIC_OF_NODES
+struct of_changeset;
+#endif
 
 /* struct pci_dev - describes a PCI device
  *
@@ -598,6 +601,10 @@ struct pci_dev {
 	u8		tph_mode;	/* TPH mode */
 	u8		tph_req_type;	/* TPH requester type */
 #endif
+
+#ifdef CONFIG_PCI_DYNAMIC_OF_NODES
+	struct of_changeset *cset; /* Changeset used for OF node creation */
+#endif
 };
 
 static inline struct pci_dev *pci_physfn(struct pci_dev *dev)
@@ -670,6 +677,10 @@ struct pci_host_bridge {
 	unsigned int	broken_l1ss_resume:1;	/* Resuming from L1SS during
 						   system suspend is broken */
 
+#ifdef CONFIG_PCI_DYNAMIC_OF_NODES
+	struct of_changeset *cset; /* Changeset used for OF node creation */
+#endif
+
 	/* Resource alignment requirements */
 	resource_size_t (*align_resource)(struct pci_dev *dev,
 			const struct resource *res,
-- 
2.55.0