linux-kernel - RE: [PATCH v9 03/17] platform/x86: dell-wmi: clean up wmi descriptor check

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Date:   Tue, 17 Oct 2017 19:31:13 +0000
From:   <Mario.Limonciello@...l.com>
To:     <pali.rohar@...il.com>
CC:     <dvhart@...radead.org>, <andy.shevchenko@...il.com>,
        <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <luto@...nel.org>,
        <quasisec@...gle.com>, <rjw@...ysocki.net>, <mjg59@...gle.com>,
        <hch@....de>, <greg@...ah.com>, <gnomes@...rguk.ukuu.org.uk>
Subject: RE: [PATCH v9 03/17] platform/x86: dell-wmi: clean up wmi descriptor
 check

> -----Original Message-----
> From: Pali Rohár [mailto:pali.rohar@...il.com]
> Sent: Tuesday, October 17, 2017 1:45 PM
> To: Limonciello, Mario <Mario_Limonciello@...l.com>
> Cc: dvhart@...radead.org; Andy Shevchenko <andy.shevchenko@...il.com>;
> LKML <linux-kernel@...r.kernel.org>; platform-driver-x86@...r.kernel.org; Andy
> Lutomirski <luto@...nel.org>; quasisec@...gle.com; rjw@...ysocki.net;
> mjg59@...gle.com; hch@....de; Greg KH <greg@...ah.com>; Alan Cox
> <gnomes@...rguk.ukuu.org.uk>
> Subject: Re: [PATCH v9 03/17] platform/x86: dell-wmi: clean up wmi descriptor
> check
> 
> On Tuesday 17 October 2017 13:21:47 Mario Limonciello wrote:
> > Some cases the wrong type was used for errors and checks can be
> > done more cleanly.
> >
> > Signed-off-by: Mario Limonciello <mario.limonciello@...l.com>
> > Reviewed-by: Edward O'Callaghan <quasisec@...gle.com>
> > Suggested-by: Andy Shevchenko <andy.shevchenko@...il.com>
> > ---
> >  drivers/platform/x86/dell-wmi.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/platform/x86/dell-wmi.c b/drivers/platform/x86/dell-wmi.c
> > index 2cfaaa8faf0a..ece2fe341f01 100644
> > --- a/drivers/platform/x86/dell-wmi.c
> > +++ b/drivers/platform/x86/dell-wmi.c
> > @@ -663,19 +663,19 @@ static int dell_wmi_check_descriptor_buffer(struct
> wmi_device *wdev)
> >
> >  	buffer = (u32 *)obj->buffer.pointer;
> >
> > -	if (buffer[0] != 0x4C4C4544 && buffer[1] != 0x494D5720) {
> > -		dev_err(&wdev->dev, "Dell descriptor buffer has invalid signature
> (%*ph)\n",
> > -			8, buffer);
> > +	if (strncmp(obj->string.pointer, "DELL WMI", 8) != 0) {
> > +		dev_err(&wdev->dev, "Dell descriptor buffer has invalid signature
> (%8ph)\n",
> > +			buffer);
> >  		ret = -EINVAL;
> >  		goto out;
> >  	}
> >
> >  	if (buffer[2] != 0 && buffer[2] != 1)
> > -		dev_warn(&wdev->dev, "Dell descriptor buffer has unknown
> version (%d)\n",
> > +		dev_warn(&wdev->dev, "Dell descriptor buffer has unknown
> version (%u)\n",
> >  			buffer[2]);
> 
> To be correct, buffer[2] is of type "u32", not of type "unsigned". So
> this patch does not fix it properly.
> 

What's the proper solution then?  
Cast buffer[2] to a known type length like unsigned long and use %lu?