firewire: nosy: do not ignore errors in ioremap_nocache()

There is no check if ioremap_nocache() returns a valid pointer.
Potentially it can lead to null pointer dereference.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (renamed goto labels)

drivers/firewire/nosy.c

@@ -566,6 +566,11 @@ add_card(struct pci_dev *dev, const struct pci_device_id *unused)
 
 	lynx->registers = ioremap_nocache(pci_resource_start(dev, 0),
 					  PCILYNX_MAX_REGISTER);
+	if (lynx->registers == NULL) {
+		dev_err(&dev->dev, "Failed to map registers\n");
+		ret = -ENOMEM;
+		goto fail_deallocate_lynx;
+	}
 
 	lynx->rcv_start_pcl = pci_alloc_consistent(lynx->pci_device,
 				sizeof(struct pcl), &lynx->rcv_start_pcl_bus);
@@ -578,7 +583,7 @@ add_card(struct pci_dev *dev, const struct pci_device_id *unused)
 	    lynx->rcv_buffer == NULL) {
 		dev_err(&dev->dev, "Failed to allocate receive buffer\n");
 		ret = -ENOMEM;
-		goto fail_deallocate;
+		goto fail_deallocate_buffers;
 	}
 	lynx->rcv_start_pcl->next	= cpu_to_le32(lynx->rcv_pcl_bus);
 	lynx->rcv_pcl->next		= cpu_to_le32(PCL_NEXT_INVALID);
@@ -641,7 +646,7 @@ add_card(struct pci_dev *dev, const struct pci_device_id *unused)
 		dev_err(&dev->dev,
 			"Failed to allocate shared interrupt %d\n", dev->irq);
 		ret = -EIO;
-		goto fail_deallocate;
+		goto fail_deallocate_buffers;
 	}
 
 	lynx->misc.parent = &dev->dev;
@@ -668,7 +673,7 @@ add_card(struct pci_dev *dev, const struct pci_device_id *unused)
 	reg_write(lynx, PCI_INT_ENABLE, 0);
 	free_irq(lynx->pci_device->irq, lynx);
 
-fail_deallocate:
+fail_deallocate_buffers:
 	if (lynx->rcv_start_pcl)
 		pci_free_consistent(lynx->pci_device, sizeof(struct pcl),
 				lynx->rcv_start_pcl, lynx->rcv_start_pcl_bus);
@@ -679,6 +684,8 @@ add_card(struct pci_dev *dev, const struct pci_device_id *unused)
 		pci_free_consistent(lynx->pci_device, PAGE_SIZE,
 				lynx->rcv_buffer, lynx->rcv_buffer_bus);
 	iounmap(lynx->registers);
+
+fail_deallocate_lynx:
 	kfree(lynx);
 
 fail_disable: