cxl: Check if vphb exists before iterating over AFU devices

During an eeh a kernel-oops is reported if no vPHB is allocated to the
AFU. This happens as during AFU init, an error in creation of vPHB is
a non-fatal error. Hence afu->phb should always be checked for NULL
before iterating over it for the virtual AFU pci devices.

This patch fixes the kenel-oops by adding a NULL pointer check for
afu->phb before it is dereferenced.

Fixes: 9e8df8a21963 ("cxl: EEH support")
Cc: stable@vger.kernel.org # v4.3+
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 10 insertions, 2 deletions

diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index bb7fd3f4edab..19969ee86d6f 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -2083,6 +2083,9 @@ static pci_ers_result_t cxl_vphb_error_detected(struct cxl_afu *afu,
         /* There should only be one entry, but go through the list
          * anyway
          */
+        if (afu->phb == NULL)
+                return result;
+
         list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) {
                 if (!afu_dev->driver)
                         continue;
@@ -2124,8 +2127,7 @@ static pci_ers_result_t cxl_pci_error_detected(struct pci_dev *pdev,
                          * Tell the AFU drivers; but we don't care what they
                          * say, we're going away.
                          */
-                        if (afu->phb != NULL)
-                                cxl_vphb_error_detected(afu, state);
+                        cxl_vphb_error_detected(afu, state);
                 }
                 return PCI_ERS_RESULT_DISCONNECT;
         }
@@ -2265,6 +2267,9 @@ static pci_ers_result_t cxl_pci_slot_reset(struct pci_dev *pdev)
                 if (cxl_afu_select_best_mode(afu))
                         goto err;
 
+                if (afu->phb == NULL)
+                        continue;
+
                 list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) {
                         /* Reset the device context.
                          * TODO: make this less disruptive
@@ -2327,6 +2332,9 @@ static void cxl_pci_resume(struct pci_dev *pdev)
         for (i = 0; i < adapter->slices; i++) {
                 afu = adapter->afu[i];
 
+                if (afu->phb == NULL)
+                        continue;
+
                 list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) {
                         if (afu_dev->driver && afu_dev->driver->err_handler &&
                             afu_dev->driver->err_handler->resume)