[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

1 files changed, 22 insertions, 0 deletions

diff --git a/llvm/lib/Object/COFFObjectFile.cpp b/llvm/lib/Object/COFFObjectFile.cpp
index b3dbf75a5c3..368a6d10344 100644
--- a/llvm/lib/Object/COFFObjectFile.cpp
+++ b/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));
+}