From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753430Ab2IXFo6 (ORCPT ); Mon, 24 Sep 2012 01:44:58 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:35494 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751325Ab2IXFo5 (ORCPT ); Mon, 24 Sep 2012 01:44:57 -0400 Message-ID: <1348465493.2467.3.camel@dabdike> Subject: Re: [PATCH scsi] Add NULL checking of return value from scsi_cmd_to_driver() From: James Bottomley To: Li Zhong Cc: LKML , linux-scsi@vger.kernel.org, "Paul E. McKenney" Date: Mon, 24 Sep 2012 09:44:53 +0400 In-Reply-To: <1348464626.2475.13.camel@ThinkPad-T420> References: <1348464626.2475.13.camel@ThinkPad-T420> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2012-09-24 at 13:30 +0800, Li Zhong wrote: > Just noticed that after commit 919f797, it is possible that > scsi_cmd_to_driver() returns NULL. This patch adds the NULL checking for drv > returned from the above function. > > Maybe it is not possible at run time, but from the code itself, we'd better > have this check? There's not much point having a check that never trips, unless it's an assert, in which case a NULL deref does that. All it does is add pointless instructions to the critical path. only REQ_TYPE_BLOCK_PC commands can be submitted without a driver, so the check above would seem to preclude that. James