EXT-4388 Crash in octree line segment intersection code

a more complete fix and some sanity to prevent recurrance of a similar problem.

reviewed by bao!

indra/llrender/llimagegl.cpp

@@ -436,6 +436,8 @@ void LLImageGL::init(BOOL usemipmaps)
 	mLastBindTime = 0.f;
 
 	mPickMask = NULL;
+	mPickMaskWidth = 0;
+	mPickMaskHeight = 0;
 	mUseMipMaps = usemipmaps;
 	mHasExplicitFormat = FALSE;
 	mAutoGenMips = FALSE;
@@ -528,6 +530,11 @@ void LLImageGL::setSize(S32 width, S32 height, S32 ncomponents)
 			destroyGLTexture();
 		}
 
+		// pickmask validity depends on old image size, delete it
+		delete [] mPickMask;
+		mPickMask = NULL;
+		mPickMaskWidth = mPickMaskHeight = 0;
+
 		mWidth = width;
 		mHeight = height;
 		mComponents = ncomponents;
@@ -1675,12 +1682,14 @@ void LLImageGL::updatePickMask(S32 width, S32 height, const U8* data_in)
 		return ;
 	}
 
+	delete [] mPickMask;
+	mPickMask = NULL;
+	mPickMaskWidth = mPickMaskHeight = 0;
+
 	if (mFormatType != GL_UNSIGNED_BYTE ||
 	    mFormatPrimary != GL_RGBA)
 	{
 		//cannot generate a pick mask for this texture
-		delete [] mPickMask;
-		mPickMask = NULL;
 		return;
 	}
 
@@ -1688,11 +1697,10 @@ void LLImageGL::updatePickMask(S32 width, S32 height, const U8* data_in)
 	U32 pick_height = height/2;
 
 	U32 size = llmax(pick_width, (U32) 1) * llmax(pick_height, (U32) 1);
-
 	size = size/8 + 1;
-
-	delete[] mPickMask;
 	mPickMask = new U8[size];
+	mPickMaskWidth = pick_width;
+	mPickMaskHeight = pick_height;
 
 	memset(mPickMask, 0, sizeof(U8) * size);
 
@@ -1727,35 +1735,34 @@ BOOL LLImageGL::getMask(const LLVector2 &tc)
 
 	if (mPickMask)
 	{
-		S32 width = getWidth()/2;
-		S32 height = getHeight()/2;
-
 		F32 u = tc.mV[0] - floorf(tc.mV[0]);
 		F32 v = tc.mV[1] - floorf(tc.mV[1]);
 
-		if (u < 0.f || u > 1.f ||
-		    v < 0.f || v > 1.f)
+		if (LL_UNLIKELY(u < 0.f || u > 1.f ||
+				v < 0.f || v > 1.f))
 		{
 			LL_WARNS_ONCE("render") << "Ugh, u/v out of range in image mask pick" << LL_ENDL;
 			u = v = 0.f;
 			llassert(false);
 		}
 
-		S32 x = (S32)(u * width);
-		S32 y = (S32)(v * height);
+		llassert(mPickMaskWidth > 0 && mPickMaskHeight > 0);
+		
+		S32 x = (S32)(u * mPickMaskWidth);
+		S32 y = (S32)(v * mPickMaskHeight);
 
-		if (x >= width)
+		if (LL_UNLIKELY(x >= mPickMaskWidth))
 		{
 			LL_WARNS_ONCE("render") << "Ooh, width overrun on pick mask read, that coulda been bad." << LL_ENDL;
-			x = llmax(0, width-1);
+			x = llmax(0, mPickMaskWidth-1);
 		}
-		if (y >= height)
+		if (LL_UNLIKELY(y >= mPickMaskHeight))
 		{
 			LL_WARNS_ONCE("render") << "Ooh, height overrun on pick mask read, that woulda been bad." << LL_ENDL;
-			y = llmax(0, height-1);
+			y = llmax(0, mPickMaskHeight-1);
 		}
 
-		S32 idx = y*width+x;
+		S32 idx = y*mPickMaskWidth+x;
 		S32 offset = idx%8;
 
 		res = mPickMask[idx/8] & (1 << offset) ? TRUE : FALSE;

indra/llrender/llimagegl.h

@@ -193,6 +193,8 @@ class LLImageGL : public LLRefCount
 private:
 	LLPointer<LLImageRaw> mSaveData; // used for destroyGL/restoreGL
 	U8* mPickMask;  //downsampled bitmap approximation of alpha channel.  NULL if no alpha channel
+	U16 mPickMaskWidth;
+	U16 mPickMaskHeight;
 	S8 mUseMipMaps;
 	S8 mHasExplicitFormat; // If false (default), GL format is f(mComponents)
 	S8 mAutoGenMips;