4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Donnellan <andrew.donnel...@au1.ibm.com>

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.

Signed-off-by: Andrew Donnellan <andrew.donnel...@au1.ibm.com>
Reviewed-by: Matthew R. Ochs <mro...@linux.vnet.ibm.com>
Acked-by: Ian Munsie <imun...@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

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

--- a/drivers/misc/cxl/vphb.c
+++ b/drivers/misc/cxl/vphb.c
@@ -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)
--- a/drivers/pci/host-bridge.c
+++ b/drivers/pci/host-bridge.c
@@ -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)


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