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

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Date:	Tue, 31 Aug 2010 10:33:52 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Vasiliy Kulikov <segooon@...il.com>
Cc:	Julia Lawall <julia@...u.dk>, walter harms <wharms@....de>,
	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

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.

g.
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