Re: [PATCH 3/6] drm: Verify gamma/degamma LUT size

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Mar 01, 2018 at 06:43:21PM +0530, Sharma, Shashank wrote:
> Regards
> 
> Shashank
> 
> 
> On 2/24/2018 12:55 AM, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > While we want to potentially support multiple different gamma/degamma
> > LUT sizes we can (and should) at least check that the blob length
> > is a multiple of the LUT entry size.
> I dint understand the exact idea behind doing this, how is this going to 
> benefit ? May be a bit more description ?

The benefit is rejecting garbage fed in from userspace.

> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >   drivers/gpu/drm/drm_atomic.c | 15 +++++++++++----
> >   1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 8945357212ba..933edec0299d 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -413,6 +413,7 @@ drm_atomic_replace_property_blob_from_id(struct drm_device *dev,
> >   					 struct drm_property_blob **blob,
> >   					 uint64_t blob_id,
> >   					 ssize_t expected_size,
> > +					 ssize_t expected_size_mod,
> >   					 bool *replaced)
> >   {
> >   	struct drm_property_blob *new_blob = NULL;
> > @@ -422,7 +423,13 @@ drm_atomic_replace_property_blob_from_id(struct drm_device *dev,
> >   		if (new_blob == NULL)
> >   			return -EINVAL;
> >   
> > -		if (expected_size > 0 && expected_size != new_blob->length) {
> > +		if (expected_size > 0 &&
> > +		    new_blob->length != expected_size) {
> > +			drm_property_blob_put(new_blob);
> > +			return -EINVAL;
> > +		}
> One line needed here, matching the previous if() pattern

What line? Don't understand.

> > +		if (expected_size_mod > 0 &&
> > +		    new_blob->length % expected_size_mod != 0) {
> >   			drm_property_blob_put(new_blob);
> >   			return -EINVAL;
> >   		}
> > @@ -470,7 +477,7 @@ int drm_atomic_crtc_set_property(struct drm_crtc *crtc,
> >   		ret = drm_atomic_replace_property_blob_from_id(dev,
> >   					&state->degamma_lut,
> >   					val,
> > -					-1,
> > +					-1, sizeof(struct drm_color_lut),
> >   					&replaced);
> >   		state->color_mgmt_changed |= replaced;
> >   		return ret;
> > @@ -478,7 +485,7 @@ int drm_atomic_crtc_set_property(struct drm_crtc *crtc,
> >   		ret = drm_atomic_replace_property_blob_from_id(dev,
> >   					&state->ctm,
> >   					val,
> > -					sizeof(struct drm_color_ctm),
> > +					sizeof(struct drm_color_ctm), -1,
> >   					&replaced);
> >   		state->color_mgmt_changed |= replaced;
> >   		return ret;
> > @@ -486,7 +493,7 @@ int drm_atomic_crtc_set_property(struct drm_crtc *crtc,
> >   		ret = drm_atomic_replace_property_blob_from_id(dev,
> >   					&state->gamma_lut,
> >   					val,
> > -					-1,
> > +					-1, sizeof(struct drm_color_lut),
> >   					&replaced);
> >   		state->color_mgmt_changed |= replaced;
> >   		return ret;

-- 
Ville Syrjälä
Intel OTC
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