net: fujitsu: fix potential null-ptr-deref

In fmvj18x_get_hwinfo(), if ioremap fails there will be NULL pointer
deref. To fix this, check the return value of ioremap and return -1
to the caller in case of failure.

Cc: "David S. Miller" <davem@davemloft.net>
Acked-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
Link: https://lore.kernel.org/r/20210503115736.2104747-16-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/fujitsu/fmvj18x_cs.c

@@ -547,6 +547,11 @@ static int fmvj18x_get_hwinfo(struct pcmcia_device *link, u_char *node_id)
 	return -1;
 
     base = ioremap(link->resource[2]->start, resource_size(link->resource[2]));
+    if (!base) {
+	pcmcia_release_window(link, link->resource[2]);
+	return -1;
+    }
+
     pcmcia_map_mem_page(link, link->resource[2], 0);
 
     /*