[coreboot] [PATCH] more intelligent cbfs walker

Myles Watson mylesgw at gmail.com
Sat Apr 25 15:22:17 CEST 2009

> -----Original Message-----
> From: Patrick Georgi [mailto:patrick at georgi-clan.de]
> Sent: Saturday, April 25, 2009 7:16 AM
> To: Myles Watson
> Cc: coreboot at coreboot.org
> Subject: Re: [coreboot] [PATCH] more intelligent cbfs walker
> Am 25.04.2009 15:06, schrieb Myles Watson:
> > OK. I think that would be more clear if we tested foffset. How about
> > if (foffset == 0) /* Invalid CBFS entry that would cause an infinite
> loop */
> > 	return NULL;
> >
> > Or we could just test foffset when we test the magic number.
> >
> The problem is that we can't trust _anything_ in that array: there's no
> final entry in the chain, so the data after that is garbage.
> You still have an endless loop for (foffset == 4) && (flen == -4)
> We could do
> if (foffset + flen == 0) return NULL;
> but I wonder why we shouldn't just do the full test then, with some
> comment to the same effect as yours above.

I can see your point, but CBFS design assumes that CBFS magic is sufficient.
We know how large the file system is, and any entry inside it was created by
a CBFS tool.  If we really want to be paranoid, you need to check that
offset > oldoffset so that you don't get a negative foffset.


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