The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 12841f87b7a8ceb3d54f171660f72a86941bfcb3 Mon Sep 17 00:00:00 2001

From: Vaibhav Jain vaibhav@linux.vnet.ibm.com Date: Thu, 23 Nov 2017 09:08:57 +0530 Subject: [PATCH] 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

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)