[bitcode reader] Fix an assert on invalid type tables

Bug found with afl-fuzz

llvm-svn: 227566

2 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 9e27225df79..c3589bce398 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1095,8 +1095,10 @@ std::error_code BitcodeReader::ParseTypeTableBody() {
 
     if (NumRecords >= TypeList.size())
       return Error("Invalid TYPE table");
+    if (TypeList[NumRecords])
+      return Error(
+          "Invalid TYPE table: Only named structs can be forward referenced");
     assert(ResultTy && "Didn't read a type?");
-    assert(!TypeList[NumRecords] && "Already read type?");
     TypeList[NumRecords++] = ResultTy;
   }
 }
diff --git a/llvm/test/Bitcode/Inputs/invalid-type-table-forward-ref.bc b/llvm/test/Bitcode/Inputs/invalid-type-table-forward-ref.bc
new file mode 100644
index 00000000000..4594efefd6c
--- /dev/null
+++ b/llvm/test/Bitcode/Inputs/invalid-type-table-forward-ref.bc