[PATCH] cxl: Check if vphb exists before iterating over AFU devices

[Vaibhav Jain]

commit 12841f87b7a8ceb3d54f171660f72a86941bfcb3 upstream, for 4.3.

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: sta...@vger.kernel.org # v4.3+
Signed-off-by: Vaibhav Jain <vaib...@linux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnel...@au1.ibm.com>
Acked-by: Frederic Barrat <fbar...@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
Changelog:
- Rebased the patch on 4.3 stable tree
---
 drivers/misc/cxl/pci.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 85761d7eb333..b982329f3837 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -1328,6 +1328,9 @@ 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;
@@ -1368,6 +1371,10 @@ static pci_ers_result_t cxl_pci_error_detected(struct 
pci_dev *pdev,
                 */
                for (i = 0; i < adapter->slices; i++) {
                        afu = adapter->afu[i];
+                       /*
+                        * Tell the AFU drivers; but we don't care what they
+                        * say, we're going away.
+                        */
                        cxl_vphb_error_detected(afu, state);
                }
                return PCI_ERS_RESULT_DISCONNECT;
@@ -1491,6 +1498,9 @@ 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;
+
                cxl_pci_vphb_reconfigure(afu);
 
                list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) 
{
@@ -1555,6 +1565,9 @@ 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)
-- 
2.14.3