From 0ed3459dbfc4b57c20c2cffeed7538fb2de8e20b Mon Sep 17 00:00:00 2001
From: caheckman <48068198+caheckman@users.noreply.github.com>
Date: Thu, 4 Jan 2024 22:57:33 +0000
Subject: [PATCH] GP-4201 Check for descendants prior to normalizeReadSize

---
 .../Decompiler/src/decompile/cpp/heritage.cc    | 17 ++++++++++-------
 .../Decompiler/src/decompile/cpp/heritage.hh    |  2 +-
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/Ghidra/Features/Decompiler/src/decompile/cpp/heritage.cc b/Ghidra/Features/Decompiler/src/decompile/cpp/heritage.cc
index 30a8959dd3..d6ca0cb615 100644
--- a/Ghidra/Features/Decompiler/src/decompile/cpp/heritage.cc
+++ b/Ghidra/Features/Decompiler/src/decompile/cpp/heritage.cc
@@ -331,20 +331,17 @@ bool Heritage::callOpIndirectEffect(const Address &addr,int4 size,PcodeOp *op) c
 /// of the address range currently being linked, create a Varnode of
 /// the correct size and define the original Varnode as a SUBPIECE.
 /// \param vn is the given too small Varnode
+/// \param op is the reading PcodeOp
 /// \param addr is the start of the (larger) range
 /// \param size is the number of bytes in the range
 /// \return the new larger Varnode
-Varnode *Heritage::normalizeReadSize(Varnode *vn,const Address &addr,int4 size)
+Varnode *Heritage::normalizeReadSize(Varnode *vn,PcodeOp *op,const Address &addr,int4 size)
 
 {
   int4 overlap;
   Varnode *vn1,*vn2;
-  PcodeOp *op,*newop;
+  PcodeOp *newop;
 
-  list<PcodeOp *>::const_iterator oiter = vn->beginDescend();
-  op = *oiter++;
-  if (oiter != vn->endDescend())
-    throw LowlevelError("Free varnode with multiple reads");
   newop = fd->newOp(2,op->getAddr());
   fd->opSetOpcode(newop,CPUI_SUBPIECE);
   vn1 = fd->newVarnode(size,addr);
@@ -1122,8 +1119,14 @@ void Heritage::guard(const Address &addr,int4 size,bool guardPerformed,
 
   for(iter=read.begin();iter!=read.end();++iter) {
     vn = *iter;
+    list<PcodeOp *>::const_iterator oiter = vn->beginDescend();
+    if (oiter == vn->endDescend())	// removeRevisitedMarkers may have eliminated descendant
+      continue;
+    PcodeOp *op = *oiter++;
+    if (oiter != vn->endDescend())
+      throw LowlevelError("Free varnode with multiple reads");
     if (vn->getSize() < size)
-      *iter = vn = normalizeReadSize(vn,addr,size);
+      *iter = vn = normalizeReadSize(vn,op,addr,size);
     vn->setActiveHeritage();
   }
 
diff --git a/Ghidra/Features/Decompiler/src/decompile/cpp/heritage.hh b/Ghidra/Features/Decompiler/src/decompile/cpp/heritage.hh
index b488a25235..a309fb27aa 100644
--- a/Ghidra/Features/Decompiler/src/decompile/cpp/heritage.hh
+++ b/Ghidra/Features/Decompiler/src/decompile/cpp/heritage.hh
@@ -235,7 +235,7 @@ class Heritage {
   void removeRevisitedMarkers(const vector<Varnode *> &remove,const Address &addr,int4 size);
   int4 collect(Address addr,int4 size,vector<Varnode *> &read,vector<Varnode *> &write,vector<Varnode *> &input,vector<Varnode *> &remove) const;
   bool callOpIndirectEffect(const Address &addr,int4 size,PcodeOp *op) const;
-  Varnode *normalizeReadSize(Varnode *vn,const Address &addr,int4 size);
+  Varnode *normalizeReadSize(Varnode *vn,PcodeOp *op,const Address &addr,int4 size);
   Varnode *normalizeWriteSize(Varnode *vn,const Address &addr,int4 size);
   Varnode *concatPieces(const vector<Varnode *> &vnlist,PcodeOp *insertop,Varnode *finalvn);
   void splitPieces(const vector<Varnode *> &vnlist,PcodeOp *insertop,const Address &addr,int4 size,Varnode *startvn);