CVE-2018-8629 OOB bug in Edge WIP

Author: rajatd

lib/Backend/FlowGraph.cpp

@@ -5266,7 +5266,7 @@ BasicBlock::MergePredBlocksValueMaps(GlobOpt* globOpt)
             }
             if(symsRequiringCompensationToMergedValueInfoMap.Count() != 0)
             {
-                globOpt->InsertValueCompensation(pred, symsRequiringCompensationToMergedValueInfoMap);
+                globOpt->InsertValueCompensation(pred, &symsRequiringCompensationToMergedValueInfoMap);
             }
         }
     } NEXT_PREDECESSOR_EDGE_EDITING;
@@ -5325,6 +5325,12 @@ BasicBlock::MergePredBlocksValueMaps(GlobOpt* globOpt)
         loop->liveFieldsOnEntry = JitAnew(globOpt->alloc, BVSparse<JitArenaAllocator>, globOpt->alloc);
         loop->liveFieldsOnEntry->Copy(this->globOptData.liveFields);
 
+        if (symsRequiringCompensationToMergedValueInfoMap.Count() != 0)
+        {
+            loop->symsRequiringCompensationToMergedValueInfoMap = JitAnew(globOpt->alloc, SymToValueInfoMap, globOpt->alloc);
+            loop->symsRequiringCompensationToMergedValueInfoMap->Copy(&symsRequiringCompensationToMergedValueInfoMap);
+        }
+        
         if(globOpt->DoBoundCheckHoist() && loop->inductionVariables)
         {
             globOpt->FinalizeInductionVariables(loop, &blockData);

lib/Backend/FlowGraph.h

@@ -575,6 +575,7 @@ class Loop
     BVSparse<JitArenaAllocator> *lossyInt32SymsOnEntry; // see GlobOptData::liveLossyInt32Syms
     BVSparse<JitArenaAllocator> *float64SymsOnEntry;
     BVSparse<JitArenaAllocator> *liveFieldsOnEntry;
+    SymToValueInfoMap           *symsRequiringCompensationToMergedValueInfoMap;
 
     BVSparse<JitArenaAllocator> *symsUsedBeforeDefined;                // stack syms that are live in the landing pad, and used before they are defined in the loop
     BVSparse<JitArenaAllocator> *likelyIntSymsUsedBeforeDefined;       // stack syms that are live in the landing pad with a likely-int value, and used before they are defined in the loop
@@ -742,7 +743,8 @@ class Loop
         allFieldsKilled(false),
         isLeaf(true),
         isProcessed(false),
-        initialValueFieldMap(alloc)
+        initialValueFieldMap(alloc),
+        symsRequiringCompensationToMergedValueInfoMap(nullptr)
     {
         this->loopNumber = ++func->loopCount;
     }

lib/Backend/GlobOpt.cpp

@@ -599,6 +599,11 @@ GlobOpt::OptBlock(BasicBlock *block)
                     this->tempBv->And(liveOnBackEdge);
                     this->ToFloat64(this->tempBv, block->loop->landingPad);
 
+                    if (block->loop->symsRequiringCompensationToMergedValueInfoMap)
+                    {
+                        InsertValueCompensation(block, block->loop->symsRequiringCompensationToMergedValueInfoMap);
+                    }
+
                     // Now that we're done with the liveFields within this loop, trim the set to those syms
                     // that the backward pass told us were live out of the loop.
                     // This assumes we have no further need of the liveFields within the loop.
@@ -1151,10 +1156,10 @@ void GlobOpt::FieldPRE(Loop *loop)
 
 void GlobOpt::InsertValueCompensation(
     BasicBlock *const predecessor,
-    const SymToValueInfoMap &symsRequiringCompensationToMergedValueInfoMap)
+    const SymToValueInfoMap *symsRequiringCompensationToMergedValueInfoMap)
 {
     Assert(predecessor);
-    Assert(symsRequiringCompensationToMergedValueInfoMap.Count() != 0);
+    Assert(symsRequiringCompensationToMergedValueInfoMap->Count() != 0);
 
     IR::Instr *insertBeforeInstr = predecessor->GetLastInstr();
     Func *const func = insertBeforeInstr->m_func;
@@ -1193,7 +1198,7 @@ void GlobOpt::InsertValueCompensation(
         }
     };
     JsUtil::List<DelayChangeValueInfo, ArenaAllocator> delayChangeValueInfo(alloc);
-    for(auto it = symsRequiringCompensationToMergedValueInfoMap.GetIterator(); it.IsValid(); it.MoveNext())
+    for(auto it = symsRequiringCompensationToMergedValueInfoMap->GetIterator(); it.IsValid(); it.MoveNext())
     {
         const auto &entry = it.Current();
         Sym *const sym = entry.Key();

lib/Backend/GlobOpt.h

@@ -737,7 +737,7 @@ class GlobOpt
     void                    PreLowerCanonicalize(IR::Instr *instr, Value **pSrc1Val, Value **pSrc2Val);
     void                    ProcessKills(IR::Instr *instr);
     void                    InsertCloneStrs(BasicBlock *toBlock, GlobOptBlockData *toData, GlobOptBlockData *fromData);
-    void                    InsertValueCompensation(BasicBlock *const predecessor, const SymToValueInfoMap &symsRequiringCompensationToMergedValueInfoMap);
+    void                    InsertValueCompensation(BasicBlock *const predecessor, const SymToValueInfoMap *symsRequiringCompensationToMergedValueInfoMap);
     IR::Instr *             ToVarUses(IR::Instr *instr, IR::Opnd *opnd, bool isDst, Value *val);
     void                    ToVar(BVSparse<JitArenaAllocator> *bv, BasicBlock *block);
     IR::Instr *             ToVar(IR::Instr *instr, IR::RegOpnd *regOpnd, BasicBlock *block, Value *val, bool needsUpdate);