linux-kernel - Re: [PATCH] target: fix crash in cmd tracing when cmd didn't match a LUN

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Message-ID: <20150724105206.GA25162@lst.de>
Date:	Fri, 24 Jul 2015 12:52:06 +0200
From:	Christoph Hellwig <hch@....de>
To:	Spencer Baugh <sbaugh@...ern.com>
Cc:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	Sagi Grimberg <sagig@...lanox.com>,
	Christoph Hellwig <hch@....de>,
	Bart Van Assche <bart.vanassche@...disk.com>,
	Alexei Potashnik <alexei@...estorage.com>,
	Andy Grover <agrover@...hat.com>,
	Christophe Vu-Brugier <cvubrugier@...tmail.fm>,
	Roland Dreier <roland@...estorage.com>,
	"open list:TARGET SUBSYSTEM" <linux-scsi@...r.kernel.org>,
	"open list:TARGET SUBSYSTEM" <target-devel@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	Joern Engel <joern@...estorage.com>,
	Spencer Baugh <Spencer.baugh@...estorage.com>
Subject: Re: [PATCH] target: fix crash in cmd tracing when cmd didn't match
	a LUN

On Thu, Jul 23, 2015 at 03:19:32PM -0700, Spencer Baugh wrote:
> From: Alexei Potashnik <alexei@...estorage.com>
> 
> If command didn't match a LUN and we're sending check condition, the
> target_cmd_complete ftrace point will crash because it assumes that
> cmd->t_task_cdb has been set.
> 
> The fix will temporarily set t_task_cdb to the se_cmd buffer
> and copy first 6 bytes of cdb in there as soon as possible.
> At a later point t_task_cdb is reset to the correct buffer,
> but until then traces and printks don't cause a crash.

This is too ugly to live.  Just dropping the t_task_cdb dereference
from the trace point sounds like the simples quick fix for now,
and removing the crazy layering violation in iSCSI that opencode
target_submit_cmd is the proper long term fix.
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