linux-kernel - [PATCH 4.4 02/78] cxl: Check if vphb exists before iterating over AFU devices

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Date:   Fri, 22 Dec 2017 09:45:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Frederic Barrat <fbarrat@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.4 02/78] cxl: Check if vphb exists before iterating over AFU devices

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

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

From: Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>

commit 12841f87b7a8ceb3d54f171660f72a86941bfcb3 upstream.

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")
Signed-off-by: Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@....ibm.com>
Acked-by: Frederic Barrat <fbarrat@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/misc/cxl/pci.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -1329,6 +1329,9 @@ static pci_ers_result_t cxl_vphb_error_d
 	/* 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;
@@ -1369,6 +1372,10 @@ static pci_ers_result_t cxl_pci_error_de
 		 */
 		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;
@@ -1492,6 +1499,9 @@ static pci_ers_result_t cxl_pci_slot_res
 		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) {
@@ -1556,6 +1566,9 @@ static void cxl_pci_resume(struct pci_de
 	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)