Message-ID: <49C89CBC.4030600@cn.fujitsu.com>
Date: Tue, 24 Mar 2009 16:41:32 +0800
From: Li Zefan <lizf@cn.fujitsu.com>
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To: Ingo Molnar <mingo@elte.hu>
CC: Jens Axboe <jens.axboe@oracle.com>, Steven Rostedt <rostedt@goodmis.org>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/5] blktrace: fix off-by-one bug
References: <49C893FC.9080905@cn.fujitsu.com> <49C89447.5060303@cn.fujitsu.com> <20090324082754.GA13016@elte.hu> <49C89ACE.9070102@cn.fujitsu.com>
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Li Zefan wrote:
>>> -	if (unlikely(what == 0 || what > ARRAY_SIZE(what2act)))
>>> +	if (unlikely(what == 0 || what >= ARRAY_SIZE(what2act)))
>> ah, nice. How did you notice - did we miss "remap" events due to 
>> this bug?
>>

forgot to mention, we didn't miss any "remap" events.

> 
> By code review, but we can get NULL dereference bug if we receive an
> "abort" event, this event may be generated only when using device-mapper.
> 

and not NULL dereference, but accessing invalid memory.

what2act["abort"]->print(...)

and "abort" == ARRAY_SIZE(what2act).

> We don't print out this event currently, neither does the userspace
> blktrace, which should be fixed.
> 


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