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

[Ben Skeggs]

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.
> 
> 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];