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

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

On Thu, Mar 01, 2018 at 07:58:07PM +0530, Sharma, Shashank wrote:
> Regards
> 
> Shashank
> 
> 
> On 3/1/2018 6:54 PM, Ville Syrjälä wrote:
> > 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.
> I mean, I can see a blank line before previous if() condition, so lets 
> keep the same pattern for this if() too

OTOH the two ifs are related so maybe just keep them together? Doesn't
actually matter to me though.

> 
> - Shashank
> >>> +		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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