[COFF] Add a bounds checking helper for iterating a coff_resource_dir_table

Instead of blindly incrementing pointers in llvm-readobj, use this
helper, which does bounds checking against the available section
data.

Differential Revision: https://reviews.llvm.org/D66818

llvm-svn: 370310

Author: mstorsjo

llvm/include/llvm/Object/COFF.h

@@ -1209,11 +1209,15 @@ class ResourceSectionRef {
   Expected<const coff_resource_dir_table &>
   getEntrySubDir(const coff_resource_dir_entry &Entry);
   Expected<const coff_resource_dir_table &> getBaseTable();
+  Expected<const coff_resource_dir_entry &>
+  getTableEntry(const coff_resource_dir_table &Table, uint32_t Index);
 
 private:
   BinaryByteStream BBS;
 
   Expected<const coff_resource_dir_table &> getTableAtOffset(uint32_t Offset);
+  Expected<const coff_resource_dir_entry &>
+  getTableEntryAtOffset(uint32_t Offset);
   Expected<ArrayRef<UTF16>> getDirStringAtOffset(uint32_t Offset);
 };
 

llvm/lib/Object/COFFObjectFile.cpp

@@ -1696,6 +1696,17 @@ ResourceSectionRef::getTableAtOffset(uint32_t Offset) {
   return *Table;
 }
 
+Expected<const coff_resource_dir_entry &>
+ResourceSectionRef::getTableEntryAtOffset(uint32_t Offset) {
+  const coff_resource_dir_entry *Entry = nullptr;
+
+  BinaryStreamReader Reader(BBS);
+  Reader.setOffset(Offset);
+  RETURN_IF_ERROR(Reader.readObject(Entry));
+  assert(Entry != nullptr);
+  return *Entry;
+}
+
 Expected<const coff_resource_dir_table &>
 ResourceSectionRef::getEntrySubDir(const coff_resource_dir_entry &Entry) {
   return getTableAtOffset(Entry.Offset.value());
@@ -1704,3 +1715,14 @@ ResourceSectionRef::getEntrySubDir(const coff_resource_dir_entry &Entry) {
 Expected<const coff_resource_dir_table &> ResourceSectionRef::getBaseTable() {
   return getTableAtOffset(0);
 }
+
+Expected<const coff_resource_dir_entry &>
+ResourceSectionRef::getTableEntry(const coff_resource_dir_table &Table,
+                                  uint32_t Index) {
+  if (Index >= (uint32_t)(Table.NumberOfNameEntries + Table.NumberOfIDEntries))
+    return createStringError(object_error::parse_failed, "index out of range");
+  const uint8_t *TablePtr = reinterpret_cast<const uint8_t *>(&Table);
+  ptrdiff_t TableOffset = TablePtr - BBS.data().data();
+  return getTableEntryAtOffset(TableOffset + sizeof(Table) +
+                               Index * sizeof(coff_resource_dir_entry));
+}

llvm/tools/llvm-readobj/COFFDumper.cpp

@@ -171,9 +171,6 @@ class COFFDumper : public ObjDumper {
   void printDelayImportedSymbols(
       const DelayImportDirectoryEntryRef &I,
       iterator_range<imported_symbol_iterator> Range);
-  Expected<const coff_resource_dir_entry &>
-  getResourceDirectoryTableEntry(const coff_resource_dir_table &Table,
-                                 uint32_t Index);
 
   typedef DenseMap<const coff_section*, std::vector<RelocationRef> > RelocMapTy;
 
@@ -1790,8 +1787,7 @@ COFFDumper::countTotalTableEntries(ResourceSectionRef RSF,
   uint32_t TotalEntries = 0;
   for (int i = 0; i < Table.NumberOfNameEntries + Table.NumberOfIDEntries;
        i++) {
-    auto Entry = unwrapOrError(Obj->getFileName(),
-                               getResourceDirectoryTableEntry(Table, i));
+    auto Entry = unwrapOrError(Obj->getFileName(), RSF.getTableEntry(Table, i));
     if (Entry.Offset.isSubDir()) {
       StringRef NextLevel;
       if (Level == "Name")
@@ -1818,8 +1814,7 @@ void COFFDumper::printResourceDirectoryTable(
   // Iterate through level in resource directory tree.
   for (int i = 0; i < Table.NumberOfNameEntries + Table.NumberOfIDEntries;
        i++) {
-    auto Entry = unwrapOrError(Obj->getFileName(),
-                               getResourceDirectoryTableEntry(Table, i));
+    auto Entry = unwrapOrError(Obj->getFileName(), RSF.getTableEntry(Table, i));
     StringRef Name;
     SmallString<20> IDStr;
     raw_svector_ostream OS(IDStr);
@@ -1873,15 +1868,6 @@ void COFFDumper::printResourceDirectoryTable(
   }
 }
 
-Expected<const coff_resource_dir_entry &>
-COFFDumper::getResourceDirectoryTableEntry(const coff_resource_dir_table &Table,
-                                           uint32_t Index) {
-  if (Index >= (uint32_t)(Table.NumberOfNameEntries + Table.NumberOfIDEntries))
-    return createError("can't get resource directory table entry");
-  auto TablePtr = reinterpret_cast<const coff_resource_dir_entry *>(&Table + 1);
-  return TablePtr[Index];
-}
-
 void COFFDumper::printStackMap() const {
   object::SectionRef StackMapSection;
   for (auto Sec : Obj->sections()) {