[POWERPC] CHRP: Fix possible NULL pointer dereference

This fixes a possible NULL pointer dereference inside of strncmp() if
of_get_property() fails.
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/platforms/chrp/setup.c

@@ -115,7 +115,7 @@ void chrp_show_cpuinfo(struct seq_file *m)
 	seq_printf(m, "machine\t\t: CHRP %s\n", model);
 
 	/* longtrail (goldengate) stuff */
-	if (!strncmp(model, "IBM,LongTrail", 13)) {
+	if (model && !strncmp(model, "IBM,LongTrail", 13)) {
 		/* VLSI VAS96011/12 `Golden Gate 2' */
 		/* Memory banks */
 		sdramen = (in_le32(gg2_pci_config_base + GG2_PCI_DRAM_CTRL)
@@ -203,15 +203,20 @@ static void __init sio_fixup_irq(const char *name, u8 device, u8 level,
 static void __init sio_init(void)
 {
 	struct device_node *root;
+	const char *model;
 
-	if ((root = of_find_node_by_path("/")) &&
-	    !strncmp(of_get_property(root, "model", NULL),
-			"IBM,LongTrail", 13)) {
+	root = of_find_node_by_path("/");
+	if (!root)
+		return;
+
+	model = of_get_property(root, "model", NULL);
+	if (model && !strncmp(model, "IBM,LongTrail", 13)) {
 		/* logical device 0 (KBC/Keyboard) */
 		sio_fixup_irq("keyboard", 0, 1, 2);
 		/* select logical device 1 (KBC/Mouse) */
 		sio_fixup_irq("mouse", 1, 12, 2);
 	}
+
 	of_node_put(root);
 }