linux-kernel - Re: [PATCH] eeepc-laptop: remove possible use of uninitialized value

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Message-ID: <CAH6sp9NtLDG4AvpTF7KzxwxVhrj8ZzNLugwoU5=YrLp65AptQQ@mail.gmail.com>
Date:	Wed, 10 Sep 2014 16:42:49 +0200
From:	Frans Klaver <fransklaver@...il.com>
To:	Darren Hart <dvhart@...radead.org>
Cc:	Paul Bolle <pebolle@...cali.nl>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Corentin Chary <corentin.chary@...il.com>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	acpi4asus-user <acpi4asus-user@...ts.sourceforge.net>,
	platform-driver-x86 <platform-driver-x86@...r.kernel.org>,
	linux-kernel@...r.kernel.org,
	Rafael Wysocki <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH] eeepc-laptop: remove possible use of uninitialized value

On Wed, Sep 10, 2014 at 5:33 AM, Darren Hart <dvhart@...radead.org> wrote:
> On Tue, Sep 09, 2014 at 10:50:08AM +0200, Paul Bolle wrote:
>> Hi Darren,
>>
>> On Sat, 2014-09-06 at 23:17 +0200, Rafael J. Wysocki wrote:
>> > On Friday, September 05, 2014 07:17:57 PM Darren Hart wrote:
>> > > On Thu, Sep 04, 2014 at 09:08:08AM +0200, Paul Bolle wrote:
>> > > [...]
>> > > >  static ssize_t store_sys_acpi(struct device *dev, int cm,
>> > > > @@ -278,12 +276,13 @@ static ssize_t store_sys_acpi(struct device *dev, int cm,
>> > > >         struct eeepc_laptop *eeepc = dev_get_drvdata(dev);
>> > > >         int rv, value;
>> > > >
>> > > > -       rv = parse_arg(buf, count, &value);
>> > > > -       if (rv > 0)
>> > > > -               value = set_acpi(eeepc, cm, value);
>> > > > +       rv = parse_arg(buf, &value);
>> > > > +       if (rv < 0)
>> > > > +               return rv;
>> > > > +       value = set_acpi(eeepc, cm, value);
>> > > >         if (value < 0)
>> > >
>> > > I suppose it's harmless, but it would be more explicit to reuse rv here instead
>> > > of value.
>>
>> Fine with me.
>>
>> > > >                 return -EIO;
>> > >
>> > > And as with Frans' version, I suggest propogating the error. We're talking about
>> > > a missing/invalid ACPI control method name here, ENODEV seems approprirate.
>> > >
>> > > Rafael, do you have a strong preference about what to return in such an event?
>> >
>> > No, I don't, although -ENXIO could be used here too.
>>
>> If you could say what value you'd like best I'll resend using that
>> value. (I don't know what the effect is of using a specific error here,
>> so I guess I'll have to bluff about it in the commit explanation.)
>
> First, I would prefer we propogate the error code rather than remap it.
>
> We could consider changing what the callee returns...
>
> #define EIO              5      /* I/O error */
> #define ENXIO            6      /* No such device or address */
> #define ENODEV          19      /* No such device */
>
> Of those, ENXIO seems like the most appropriate in this case.

Would it be fair to say that for consistency we should then also
change the return values of acpi_setter_handle()? It has the same
basic layout and checks as set_acpi() and get_acpi() have.
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