[Nouveau] [PATCH] drm/nouveau/pm: Prevent overflow in nouveau_perf_init()

[Ben Skeggs]

On Thu, 2011-06-16 at 23:40 +0100, Emil Velikov wrote:
> On Thu, 16 Jun 2011 04:43:59 +0100, Ben Skeggs <skeggsb at gmail.com> wrote:
> 
> > On Sat, 2011-06-11 at 13:30 +0100, Emil Velikov wrote:
> >> While parsing the perf table, there is no check if
> >> the num of entries read from the vbios is less than
> >> the currently allocated number.
> >>
> >> In case of a buggy vbios this will cause overwriting
> >> of kernel memory, causing aditional problems.
> >>
> >> Add a simple check in order to prevent the case
> > I've pushed this.  I'm not entirely certain we shouldn't just bail out
> > completely if this is the case, I suspect that if there's this many, the
> > VBIOS image is probably very screwed.
> >
> > This'll do for now :)
> >
> > Ben.
> 
> The case I was thinking about had a completely screwed vbios (see
> the attached dmesg) and bailing out would be a good idea.
> The main reason could have been the method used to fetch
> it as nvclock (uses PRAMIN) worked fine on the system
Ouch!  I guess all is good in that case with nouveau.vbios=PRAMIN then?

I do wonder if we should accept the PRAMIN image always, if it's
present, and ignore the checksum.  It does seem to be usually the best
image there is.

Ben.

> 
> Cheers
> Emil
> 
> 
> >>
> >> Signed-off-by: Emil Velikov <emil.l.velikov at gmail.com>
> >> ---
> >>  drivers/gpu/drm/nouveau/nouveau_perf.c |    5 +++++
> >>  1 files changed, 5 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/nouveau/nouveau_perf.c b/drivers/gpu/drm/nouveau/nouveau_perf.c
> >> index f2d98c9..b0e995f 100644
> >> --- a/drivers/gpu/drm/nouveau/nouveau_perf.c
> >> +++ b/drivers/gpu/drm/nouveau/nouveau_perf.c
> >> @@ -225,6 +225,11 @@ nouveau_perf_init(struct drm_device *dev)
> >>  		entries   = perf[2];
> >>  	}
> >>
> >> +	if (entries > NOUVEAU_PM_MAX_LEVEL) {
> >> +		NV_DEBUG(dev, "perf table has too many entries - buggy vbios?\n");
> >> +		entries = NOUVEAU_PM_MAX_LEVEL;
> >> +	}
> >> +
> >>  	entry = perf + headerlen;
> >>  	for (i = 0; i < entries; i++) {
> >>  		struct nouveau_pm_level *perflvl = &pm->perflvl[pm->nr_perflvl];
> >
> >