i7300_edac: Fix device reference count

pci_get_device() decrements the reference count of "from" (last
argument) so when we break off the loop successfully we have only one
device reference - and we don't know which device we have. If we want
a reference to each device, we must take them explicitly and let
the pci_get_device() walk complete to avoid duplicate references.

This is serious, as over-putting device references will cause
the device to eventually disappear. Without this fix, the kernel
crashes after a few insmod/rmmod cycles.

Tested on an Intel S7000FC4UR system with a 7300 chipset.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Link: http://lkml.kernel.org/r/20140224111656.09bbb7ed@endymion.delvare
Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
Cc: Doug Thompson <dougthompson@xmission.com>
Cc: stable@vger.kernel.org
Signed-off-by: Borislav Petkov <bp@suse.de>

1 files changed, 20 insertions, 18 deletions

diff --git a/drivers/edac/i7300_edac.c b/drivers/edac/i7300_edac.c
index d63f4798f7d0..57e96a3350f0 100644
--- a/drivers/edac/i7300_edac.c
+++ b/drivers/edac/i7300_edac.c
@@ -943,33 +943,35 @@ static int i7300_get_devices(struct mem_ctl_info *mci)
 
         /* Attempt to 'get' the MCH register we want */
         pdev = NULL;
-        while (!pvt->pci_dev_16_1_fsb_addr_map ||
-               !pvt->pci_dev_16_2_fsb_err_regs) {
-                pdev = pci_get_device(PCI_VENDOR_ID_INTEL,
-                                      PCI_DEVICE_ID_INTEL_I7300_MCH_ERR, pdev);
-                if (!pdev) {
-                        /* End of list, leave */
-                        i7300_printk(KERN_ERR,
-                                "'system address,Process Bus' "
-                                "device not found:"
-                                "vendor 0x%x device 0x%x ERR funcs "
-                                "(broken BIOS?)\n",
-                                PCI_VENDOR_ID_INTEL,
-                                PCI_DEVICE_ID_INTEL_I7300_MCH_ERR);
-                        goto error;
-                }
-
+        while ((pdev = pci_get_device(PCI_VENDOR_ID_INTEL,
+                                      PCI_DEVICE_ID_INTEL_I7300_MCH_ERR,
+                                      pdev))) {
                 /* Store device 16 funcs 1 and 2 */
                 switch (PCI_FUNC(pdev->devfn)) {
                 case 1:
-                        pvt->pci_dev_16_1_fsb_addr_map = pdev;
+                        if (!pvt->pci_dev_16_1_fsb_addr_map)
+                                pvt->pci_dev_16_1_fsb_addr_map =
+                                                        pci_dev_get(pdev);
                         break;
                 case 2:
-                        pvt->pci_dev_16_2_fsb_err_regs = pdev;
+                        if (!pvt->pci_dev_16_2_fsb_err_regs)
+                                pvt->pci_dev_16_2_fsb_err_regs =
+                                                        pci_dev_get(pdev);
                         break;
                 }
         }
 
+        if (!pvt->pci_dev_16_1_fsb_addr_map ||
+            !pvt->pci_dev_16_2_fsb_err_regs) {
+                /* At least one device was not found */
+                i7300_printk(KERN_ERR,
+                        "'system address,Process Bus' device not found:"
+                        "vendor 0x%x device 0x%x ERR funcs (broken BIOS?)\n",
+                        PCI_VENDOR_ID_INTEL,
+                        PCI_DEVICE_ID_INTEL_I7300_MCH_ERR);
+                goto error;
+        }
+
         edac_dbg(1, "System Address, processor bus- PCI Bus ID: %s  %x:%x\n",
                  pci_name(pvt->pci_dev_16_0_fsb_ctlr),
                  pvt->pci_dev_16_0_fsb_ctlr->vendor,