powerpc: Fix kexec with dynamic dma windows

When we kexec we look for a particular property added by the first
kernel, "linux,direct64-ddr-window-info", per-device where we already
have set up dynamic dma windows. The current code, though, wasn't
initializing the size of this property and thus when we kexec'd, we
would find the property but read uninitialized memory resulting in
garbage ddw values for the kexec'd kernel and panics. Fix this by
setting the size at enable_ddw() time and ensuring that the size of the
found property is valid at dupe_ddw_if_kexec() time.
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/iommu.c

@@ -730,16 +730,20 @@ static u64 dupe_ddw_if_kexec(struct pci_dev *dev, struct device_node *pdn)
 	pcidn = PCI_DN(dn);
 	direct64 = of_get_property(pdn, DIRECT64_PROPNAME, &len);
 	if (direct64) {
-		window = kzalloc(sizeof(*window), GFP_KERNEL);
-		if (!window) {
+		if (len < sizeof(struct dynamic_dma_window_prop)) {
 			remove_ddw(pdn);
 		} else {
-			window->device = pdn;
-			window->prop = direct64;
-			spin_lock(&direct_window_list_lock);
-			list_add(&window->list, &direct_window_list);
-			spin_unlock(&direct_window_list_lock);
-			dma_addr = direct64->dma_base;
+			window = kzalloc(sizeof(*window), GFP_KERNEL);
+			if (!window) {
+				remove_ddw(pdn);
+			} else {
+				window->device = pdn;
+				window->prop = direct64;
+				spin_lock(&direct_window_list_lock);
+				list_add(&window->list, &direct_window_list);
+				spin_unlock(&direct_window_list_lock);
+				dma_addr = direct64->dma_base;
+			}
 		}
 	}
 
@@ -833,7 +837,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	struct device_node *dn;
 	const u32 *uninitialized_var(ddr_avail);
 	struct direct_window *window;
-	struct property *uninitialized_var(win64);
+	struct property *win64;
 	struct dynamic_dma_window_prop *ddwprop;
 
 	mutex_lock(&direct_window_init_mutex);
@@ -907,6 +911,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	}
 	win64->name = kstrdup(DIRECT64_PROPNAME, GFP_KERNEL);
 	win64->value = ddwprop = kmalloc(sizeof(*ddwprop), GFP_KERNEL);
+	win64->length = sizeof(*ddwprop);
 	if (!win64->name || !win64->value) {
 		dev_info(&dev->dev,
 			"couldn't allocate property name and value\n");