From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH scsi] Add NULL checking of return value from scsi_cmd_to_driver() Date: Mon, 24 Sep 2012 09:44:53 +0400 Message-ID: <1348465493.2467.3.camel@dabdike> References: <1348464626.2475.13.camel@ThinkPad-T420> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1348464626.2475.13.camel@ThinkPad-T420> Sender: linux-kernel-owner@vger.kernel.org To: Li Zhong Cc: LKML , linux-scsi@vger.kernel.org, "Paul E. McKenney" List-Id: linux-scsi@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