linux-kernel - Re: [PATCH 1/7] drivers/macintosh/via-pmu-led.c: Add of_node

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Date:	Wed, 01 Sep 2010 17:03:06 +0200
From:	walter harms <wharms@....de>
To:	Grant Likely <grant.likely@...retlab.ca>
CC:	Vasiliy Kulikov <segooon@...il.com>, Julia Lawall <julia@...u.dk>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	kernel-janitors@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org
Subject: Re: [PATCH 1/7] drivers/macintosh/via-pmu-led.c: Add of_node_put
 to avoid memory leak



Grant Likely schrieb:
> On Tue, Aug 31, 2010 at 10:16 AM, Vasiliy Kulikov <segooon@...il.com> wrote:
>> On Tue, Aug 31, 2010 at 18:08 +0200, Julia Lawall wrote:
>>> On Tue, 31 Aug 2010, walter harms wrote:
>>>>>   if (strncmp(model, "PowerBook", strlen("PowerBook")) != 0 &&
>>>>>       strncmp(model, "iBook", strlen("iBook")) != 0 &&
>>>>>       strcmp(model, "PowerMac7,2") != 0 &&
>>>>>
>>>> is there any rule that says when to use strncmp ? it seems perfecly valid to use strcpy here
>>>> (what is done in the last cmp).
>>> Perhaps there are some characters after eg PowerBook that one doesn't want
>>> to compare with?
>> It seems to me that model has no '\0' in the end. If model is got from
>> the hardware then we should double check it - maybe harware is buggy.
>> Otherwise we'll overflow model.
> 
> Model does have \0 at the end.  This code is using strncmp to
> purposefully ignore the model suffix.
> 
>> But why strcmp(model, "PowerMac7,2")? IMO it should be replaced
>> with strncmp().
> 
> We use strcmp when parsing the device tree because the the length of
> the model property string is unknown and in most cases we *must* match
> the exact entire string, such as with this PowerMac7,2 example.  Using
> strncmp would also happen to match with something like
> "PowerMac7,2345" which is not the desired behaviour.
> 

hi Grant,
whould you mind to use you explanation as comment in the code ?
Tthat the strncpy/strcpy difference is important should be noted. that would be clearly a
bonos with further audits.

re,
 wh
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