linux-kernel - Re: [Xen-devel] [PATCH 9/9] xen/p2m/debugfs: Fix potential pointer exception.

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Message-ID: <20111003163757.GH17108@phenom.oracle.com>
Date:	Mon, 3 Oct 2011 12:37:57 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Dan Carpenter <error27@...il.com>
Subject: Re: [Xen-devel] [PATCH 9/9] xen/p2m/debugfs: Fix potential pointer
 exception.

On Fri, Sep 30, 2011 at 09:18:17AM +0100, Ian Campbell wrote:
> On Thu, 2011-09-29 at 20:52 +0100, Konrad Rzeszutek Wilk wrote:
> > We could be referencing the last + 1 element of level_name[]
> > array which would cause a pointer exception.
> 
> If we end up accessing it does that not mean something, i.e. should it
> not be a real string here and not NULL? Otherwise isn't it a bug in the
> lookup code that we end up looking there?

Yup. I altereted it per your recommendation to be "error".

> 
> I think this lookup correspond to the initialisation of lvl=4 and
> falling through the subsequent list of checks without matching one. In
> which case I think level_name[4] should be "unknown" or even "error".

Picked "error"
> 
> I don't think you can hit type_name[4] in the same way, type and
> prev_type are always one of the TYPE_* defines, which have values 0..3
> inclusive. You could make this more obvious and defend against future
> changes breaking this with:
> 	... type_name[] = {
> 		[TYPE_IDENTITY] = "identity",
> 		[TYPE_MISSING] = "missing"
> 		...
> 	};

Oooh, pretty. OK, queued another patch with that.
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