Verify sizes when trying to read a VBR

Also added an assert to ReadVBR64.

llvm-svn: 234984

llvm/include/llvm/Bitcode/BitstreamReader.h

@@ -395,6 +395,7 @@ public:
   // Read a VBR that may have a value up to 64-bits in size. The chunk size of
   // the VBR must still be <= 32 bits though.
   uint64_t ReadVBR64(unsigned NumBits) {
+    assert(NumBits <= 64 && "VBR can only be up to 64 bits in size.");
     uint32_t Piece = Read(NumBits);
     if ((Piece & (1U << (NumBits-1))) == 0)
       return uint64_t(Piece);

llvm/lib/Bitcode/Reader/BitstreamReader.cpp

@@ -62,6 +62,8 @@ static uint64_t readAbbreviatedField(BitstreamCursor &Cursor,
   case BitCodeAbbrevOp::Fixed:
     return Cursor.Read((unsigned)Op.getEncodingData());
   case BitCodeAbbrevOp::VBR:
+    if ((unsigned)Op.getEncodingData() > 64)
+      report_fatal_error("Invalid record");
     return Cursor.ReadVBR64((unsigned)Op.getEncodingData());
   case BitCodeAbbrevOp::Char6:
     return BitCodeAbbrevOp::DecodeChar6(Cursor.Read(6));

llvm/test/Bitcode/invalid.test

@@ -55,3 +55,8 @@ RUN: not llvm-dis -disable-output %p/Inputs/invalid-no-proper-module.bc 2>&1 | \
 RUN:   FileCheck --check-prefix=NO-MODULE %s
 
 NO-MODULE: Malformed IR file
+
+RUN: not llvm-dis -disable-output %p/Inputs/invalid-VBR-too-big.bc 2>&1 | \
+RUN:   FileCheck --check-prefix=HUGE-VBR %s
+
+HUGE-VBR: Invalid record