[llvm] [DWARFLibrary] Add bounds check to Contrib index (PR #76405)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-debuginfo

Author: None (DavidKorczynski)

<details>
<summary>Changes</summary>

Index should be within the range of Contrib before being used as an index.

Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=30308

---
Full diff: https://github.com/llvm/llvm-project/pull/76405.diff


1 Files Affected:

- (modified) llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp (+3) 


``````````diff
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp
index a4487e2dc21be1..208e3ac2c55343 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp
@@ -157,6 +157,9 @@ bool DWARFUnitIndex::parseImpl(DataExtractor IndexData) {
     auto Index = IndexData.getU32(&Offset);
     if (!Index)
       continue;
+    // Ensure Index is in valid range
+    if (Index > Header.NumColumns)
+      return false;
     Rows[i].Index = this;
     Rows[i].Contributions =
         std::make_unique<Entry::SectionContribution[]>(Header.NumColumns);

``````````

</details>


https://github.com/llvm/llvm-project/pull/76405