Patch "cxl: use pcibios_free_controller_deferred() when removing vPHBs" has been added to the 4.7-stable tree

This is a note to let you know that I've just added the patch titled

cxl: use pcibios_free_controller_deferred() when removing vPHBs

to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cxl-use-pcibios_free_controller_deferred-when-removing-vphbs.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Andrew Donnellan <[email protected]>
Date: Thu, 18 Aug 2016 17:35:14 +1000
Subject: cxl: use pcibios_free_controller_deferred() when removing vPHBs

From: Andrew Donnellan <[email protected]>

commit 6f38a8b9a45833495dc878c335c5431cd98a16ed upstream.

When cxl removes a vPHB, it's possible that the pci_controller may be freed before all references to the devices on the vPHB have been released. This in turn causes an invalid memory access when the devices are eventually released, as pcibios_release_device() attempts to call the phb's release_device hook.

In cxl_pci_vphb_remove(), remove the existing call to pcibios_free_controller(). Instead, use pcibios_free_controller_deferred() to free the pci_controller after all devices have been released. Export pci_set_host_bridge_release() so we can do this.

---
 drivers/misc/cxl/vphb.c   |   10 +++++++++-
 drivers/pci/host-bridge.c |    1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

@@ -243,6 +243,11 @@ int cxl_pci_vphb_add(struct cxl_afu *afu
 	if (phb->bus == NULL)
 		return -ENXIO;
 
+	/* Set release hook on root bus */
+	pci_set_host_bridge_release(to_pci_host_bridge(phb->bus->bridge),
+				    pcibios_free_controller_deferred,
+				    (void *) phb);
+
 	/* Claim resources. This might need some rework as well depending
 	 * whether we are doing probe-only or not, like assigning unassigned
 	 * resources etc...

@@ -269,7 +274,10 @@ void cxl_pci_vphb_remove(struct cxl_afu
 	afu->phb = NULL;
 
 	pci_remove_root_bus(phb->bus);
-	pcibios_free_controller(phb);
+	/*
+	 * We don't free phb here - that's handled by
+	 * pcibios_free_controller_deferred()
+	 */
 }
 
 bool cxl_pci_is_vphb_device(struct pci_dev *dev)

@@ -44,6 +44,7 @@ void pci_set_host_bridge_release(struct
 	bridge->release_fn = release_fn;
 	bridge->release_data = release_data;
 }
+EXPORT_SYMBOL_GPL(pci_set_host_bridge_release);
 
 void pcibios_resource_to_bus(struct pci_bus *bus, struct pci_bus_region *region,
 			     struct resource *res)

Patches currently in stable-queue which might be from [email protected] are

queue-4.7/cxl-use-pcibios_free_controller_deferred-when-removing-vphbs.patch queue-4.7/powerpc-pseries-use-pci_host_bridge.release_fn-to-kfree-phb.patch