[WATCHDOG] iTCO_wdt: fix memory corruption when RCBA is disabled by hardware

According to 9.1.33 on p.343 of ICH8.pdf RCBA can be disabled by
hardware if bit 0 of RCBA register is not set.

Perform correct check for this to prevent memory corruption under
some virtual machines where this feature is disabled.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Vasily Averin <vvs@openvz.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/watchdog/iTCO_wdt.c

@@ -666,6 +666,11 @@ static int __devinit iTCO_wdt_init(struct pci_dev *pdev,
 	   GCS = RCBA + ICH6_GCS(0x3410). */
 	if (iTCO_wdt_private.iTCO_version == 2) {
 		pci_read_config_dword(pdev, 0xf0, &base_address);
+		if ((base_address & 1) == 0) {
+			printk(KERN_ERR PFX "RCBA is disabled by harddware\n");
+			ret = -ENODEV;
+			goto out;
+		}
 		RCBA = base_address & 0xffffc000;
 		iTCO_wdt_private.gcs = ioremap((RCBA + 0x3410), 4);
 	}
@@ -675,7 +680,7 @@ static int __devinit iTCO_wdt_init(struct pci_dev *pdev,
 		printk(KERN_ERR PFX "failed to reset NO_REBOOT flag, "
 					"reboot disabled by hardware\n");
 		ret = -ENODEV;	/* Cannot reset NO_REBOOT bit */
-		goto out;
+		goto out_unmap;
 	}
 
 	/* Set the NO_REBOOT bit to prevent later reboots, just for sure */
@@ -686,7 +691,7 @@ static int __devinit iTCO_wdt_init(struct pci_dev *pdev,
 		printk(KERN_ERR PFX
 			"I/O address 0x%04lx already in use\n", SMI_EN);
 		ret = -EIO;
-		goto out;
+		goto out_unmap;
 	}
 	/* Bit 13: TCO_EN -> 0 = Disables TCO logic generating an SMI# */
 	val32 = inl(SMI_EN);
@@ -742,9 +747,10 @@ unreg_region:
 	release_region(TCOBASE, 0x20);
 unreg_smi_en:
 	release_region(SMI_EN, 4);
-out:
+out_unmap:
 	if (iTCO_wdt_private.iTCO_version == 2)
 		iounmap(iTCO_wdt_private.gcs);
+out:
 	pci_dev_put(iTCO_wdt_private.pdev);
 	iTCO_wdt_private.ACPIBASE = 0;
 	return ret;