scsi, pci, qdev, isa-bus, sysbus: don't let *_get_fw_dev_path return NULL

Use g_strdup rather than strdup, because the sole caller
(qdev_get_fw_dev_path_helper) assumes it gets non-NULL, and dereferences
it.  Besides, in that caller, the allocated buffer is already freed with
g_free, so it's better to allocate with a matching g_strdup.

In one case, (scsi-bus.c) it was trivial, so I replaced an snprintf+
g_strdup combination with an equivalent g_strdup_printf use.
Signed-off-by: NJim Meyering <meyering@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/ide/qdev.c

@@ -60,7 +60,7 @@ static char *idebus_get_fw_dev_path(DeviceState *dev)
     snprintf(path, sizeof(path), "%s@%d", qdev_fw_name(dev),
              ((IDEBus*)dev->parent_bus)->bus_id);
 
-    return strdup(path);
+    return g_strdup(path);
 }
 
 static int ide_qdev_init(DeviceState *qdev)

hw/isa-bus.c

@@ -236,7 +236,7 @@ static char *isabus_get_fw_dev_path(DeviceState *dev)
         snprintf(path + off, sizeof(path) - off, "@%04x", d->ioport_id);
     }
 
-    return strdup(path);
+    return g_strdup(path);
 }
 
 MemoryRegion *isa_address_space(ISADevice *dev)

hw/pci.c

@@ -1962,7 +1962,7 @@ static char *pcibus_get_fw_dev_path(DeviceState *dev)
                    PCI_SLOT(d->devfn));
     if (PCI_FUNC(d->devfn))
         snprintf(path + off, sizeof(path) + off, ",%x", PCI_FUNC(d->devfn));
-    return strdup(path);
+    return g_strdup(path);
 }
 
 static char *pcibus_get_dev_path(DeviceState *dev)

hw/qdev.c

@@ -520,7 +520,7 @@ char* qdev_get_fw_dev_path(DeviceState *dev)
 
     path[l-1] = '\0';
 
-    return strdup(path);
+    return g_strdup(path);
 }
 
 char *qdev_get_dev_path(DeviceState *dev)

hw/scsi-bus.c

@@ -1723,12 +1723,8 @@ static char *scsibus_get_dev_path(DeviceState *dev)
 static char *scsibus_get_fw_dev_path(DeviceState *dev)
 {
     SCSIDevice *d = SCSI_DEVICE(dev);
-    char path[100];
-
-    snprintf(path, sizeof(path), "channel@%x/%s@%x,%x", d->channel,
-             qdev_fw_name(dev), d->id, d->lun);
-
-    return strdup(path);
+    return g_strdup_printf("channel@%x/%s@%x,%x", d->channel,
+                           qdev_fw_name(dev), d->id, d->lun);
 }
 
 SCSIDevice *scsi_device_find(SCSIBus *bus, int channel, int id, int lun)

hw/sysbus.c

@@ -211,7 +211,7 @@ static char *sysbus_get_fw_dev_path(DeviceState *dev)
         snprintf(path + off, sizeof(path) - off, "@i%04x", s->pio[0]);
     }
 
-    return strdup(path);
+    return g_strdup(path);
 }
 
 void sysbus_add_memory(SysBusDevice *dev, target_phys_addr_t addr,