linux-kernel - Re: out-of-bounds array index

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Message-ID: <20080207200121.GO15220@kernel.dk>
Date:	Thu, 7 Feb 2008 21:01:22 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Jesse Barnes <jesse.barnes@...el.com>
Cc:	Jan Engelhardt <jengelh@...putergmbh.de>,
	linux-kernel@...r.kernel.org
Subject: Re: out-of-bounds array index

On Thu, Feb 07 2008, Jesse Barnes wrote:
> On Thursday, February 07, 2008 11:21 am Jan Engelhardt wrote:
> > On Feb 7 2008 19:56, Jens Axboe wrote:
> > >Just saw this from gcc:
> > >
> > >drivers/char/drm/i915_drv.c: In function ?i915_suspend?:
> > >drivers/char/drm/i915_drv.c:173: warning: array subscript is above array
> > >bounds
> > >  CC [M]  drivers/char/drm/i915_dma.o
> > >drivers/char/drm/i915_drv.c: In function ?i915_resume?:
> > >drivers/char/drm/i915_drv.c:220: warning: array subscript is above array
> > >bounds
> > >
> > >It's this code:
> > >
> > >        dev_priv->saveGR[0x18] =
> > >                i915_read_indexed(VGA_GR_INDEX, VGA_GR_DATA, 0x18);
> > >
> > >which looks legit, since saveGR is
> >
> > It is not legit at all. 0x18 is the 25th position in the array,
> > but it is only 24 big. (Excluding play-hide-and-seek games like
> > allocating more in case of malloc or char *foo[0].)
> 
> I think he was saying that the warning was legit.  Anyway, my gcc isn't smart 
> enough to emit warnings like this, maybe it's time to ugprade...

of course, the reference was to the warning (I do know C and array
indexing 101 :-)

-- 
Jens Axboe

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