cifs: check for NULL session password

commit 24e6cf92 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

fs/cifs/connect.c

@@ -1605,6 +1605,7 @@ cifs_find_smb_ses(struct TCP_Server_Info *server, struct smb_vol *vol)
 				    MAX_USERNAME_SIZE))
 				continue;
 			if (strlen(vol->username) != 0 &&
+			    ses->password != NULL &&
 			    strncmp(ses->password,
 				    vol->password ? vol->password : "",
 				    MAX_PASSWORD_SIZE))