[ganesh] Check index count for overflow for good measure

Bug: b/381696867
Bug: b/381679570
Change-Id: Ica573d9143bf204015f905efecc45983177dfe83
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/926176
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>

src/gpu/ganesh/ops/GrOvalOpFactory.cpp

@@ -22,6 +22,7 @@
 #include "include/private/base/SkFloatingPoint.h"
 #include "include/private/base/SkOnce.h"
 #include "include/private/base/SkTArray.h"
+#include "include/private/base/SkTo.h"
 #include "include/private/gpu/ganesh/GrTypesPriv.h"
 #include "src/base/SkArenaAlloc.h"
 #include "src/core/SkMatrixPriv.h"
@@ -61,6 +62,7 @@
 
 #include <algorithm>
 #include <array>
+#include <climits>
 #include <cstdint>
 #include <memory>
 #include <utility>
@@ -2831,8 +2833,11 @@ class CircularRRectOp final : public GrMeshDrawOp {
     CombineResult onCombineIfPossible(GrOp* t, SkArenaAlloc*, const GrCaps& caps) override {
         CircularRRectOp* that = t->cast<CircularRRectOp>();
 
-        // can only represent 65535 unique vertices with 16-bit indices
-        if (fVertCount + that->fVertCount > 65536) {
+        // Cannot combine if the net number of indices would overflow int32, or if the net number
+        // of vertices would overflow uint16 (since the index values are 16-bit that point into
+        // the vertex buffer).
+        if ((fIndexCount > INT32_MAX - that->fIndexCount) ||
+            (fVertCount > SkToInt(UINT16_MAX) - that->fVertCount)) {
             return CombineResult::kCannotCombine;
         }
 

src/gpu/ganesh/ops/ShadowRRectOp.cpp

@@ -51,6 +51,7 @@
 
 #include <algorithm>
 #include <array>
+#include <climits>
 #include <cstddef>
 #include <cstdint>
 #include <tuple>
@@ -648,7 +649,8 @@ class ShadowCircularRRectOp final : public GrMeshDrawOp {
         }
 
         fMesh = target->allocMesh();
-        fMesh->setIndexed(std::move(indexBuffer), fIndexCount, firstIndex, 0, fVertCount - 1,
+        fMesh->setIndexed(std::move(indexBuffer), fIndexCount, firstIndex, 0,
+                          SkTo<uint16_t>(fVertCount - 1),
                           GrPrimitiveRestart::kNo, std::move(vertexBuffer), firstVertex);
     }
 
@@ -669,6 +671,15 @@ class ShadowCircularRRectOp final : public GrMeshDrawOp {
 
     CombineResult onCombineIfPossible(GrOp* t, SkArenaAlloc*, const GrCaps& caps) override {
         ShadowCircularRRectOp* that = t->cast<ShadowCircularRRectOp>();
+
+        // Cannot combine if the net number of indices would overflow int32, or if the net number
+        // of vertices would overflow uint16 (since the index values are 16-bit that point into
+        // the vertex buffer).
+        if ((fIndexCount > INT32_MAX - that->fIndexCount) ||
+            (fVertCount > SkToInt(UINT16_MAX) - that->fVertCount)) {
+            return CombineResult::kCannotCombine;
+        }
+
         fGeoData.push_back_n(that->fGeoData.size(), that->fGeoData.begin());
         fVertCount += that->fVertCount;
         fIndexCount += that->fIndexCount;