Re: [PATCH] firmware: dmi: Check DMI structure length

From	Jean Delvare <jdelvare@suse.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH] firmware: dmi: Check DMI structure length
Date	2017-06-01 16:50 +0200
Message-ID	<tNzAd-3MT-1@gated-at.bofh.it> (permalink)
References	<tNy1s-2YH-17@gated-at.bofh.it> <tNyb9-32h-37@gated-at.bofh.it>
Organization	SUSE Linux

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Hi Andy,

Thanks for the review.

On Thu, 1 Jun 2017 16:16:05 +0300, Andy Shevchenko wrote:
> On Thu, Jun 1, 2017 at 4:08 PM, Jean Delvare <jdelvare@suse.de> wrote:
> > Before accessing DMI data to record it for later, we should ensure
> > that the DMI structures are large enough to contain the data in
> > question.  
> 
> > -       const u8 *d = (u8 *) dm + index;
> > +       const u8 *d;  
> 
> > +       d = (u8 *) dm + index;  
> 
> I think you may leave this as is and make it compiler's burden to optimize.

Is there any benefit except making the patch smaller?

> > -       const u8 *d = (u8 *) dm + index;
> > +       const u8 *d;  
> 
> > +       d = (u8 *) dm + index;  
> 
> Ditto.
> 
> > -       int i, count = *(u8 *)(dm + 1);
> > +       int i, count;  
> 
> > +       count = *(u8 *)(dm + 1);  
> 
> Ditto.

I would expect a static code analyzer to complain about at least the
last one. Dereferencing a pointer before checking its validity is bad.

I'm not a big fan of counting of compiler optimizations to make the
code right.

-- 
Jean Delvare
SUSE L3 Support

Thread

[PATCH] firmware: dmi: Check DMI structure length Jean Delvare <jdelvare@suse.de> - 2017-06-01 15:10 +0200
  Re: [PATCH] firmware: dmi: Check DMI structure length Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-06-01 15:20 +0200
    Re: [PATCH] firmware: dmi: Check DMI structure length Jean Delvare <jdelvare@suse.de> - 2017-06-01 16:50 +0200
      Re: [PATCH] firmware: dmi: Check DMI structure length Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-06-01 18:10 +0200
        Re: [PATCH] firmware: dmi: Check DMI structure length Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-06-02 20:50 +0200
          Re: [PATCH] firmware: dmi: Check DMI structure length Jean Delvare <jdelvare@suse.de> - 2017-06-03 23:20 +0200
        Re: [PATCH] firmware: dmi: Check DMI structure length Jean Delvare <jdelvare@suse.de> - 2017-06-02 20:50 +0200
  Re: [PATCH] firmware: dmi: Check DMI structure length Mika Westerberg <mika.westerberg@linux.intel.com> - 2017-06-01 16:10 +0200

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