cifs: check for NULL session password

It's possible for a cifsSesInfo struct to have a NULL password, so we
need to check for that prior to running strncmp on it.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 18af707..ec0ea4a 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1673,6 +1673,7 @@
 				    MAX_USERNAME_SIZE))
 				continue;
 			if (strlen(vol->username) != 0 &&
+			    ses->password != NULL &&
 			    strncmp(ses->password,
 				    vol->password ? vol->password : "",
 				    MAX_PASSWORD_SIZE))