Use common parse routine to read alignment values from bitcode

While fuzzing LLVM bitcode files, I discovered that (1) the bitcode reader doesn't check that alignments are no larger than 2**29; (2) downstream code doesn't check the range; and (3) for values out of range, corresponding large memory requests (based on alignment size) will fail. This code fixes the bitcode reader to check for valid alignments, fixing this problem.

This CL fixes alignment value on global variables, functions, and instructions: alloca, load, load atomic, store, store atomic.

Patch by Karl Schimpf (kschimpf@google.com).

llvm-svn: 230180

2 files changed, 46 insertions, 14 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index bb6ba6fc6e1..3b3a6eb43d1 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -794,6 +794,16 @@ static Attribute::AttrKind GetAttrFromCode(uint64_t Code) {
   }
 }
 
+std::error_code BitcodeReader::parseAlignmentValue(uint64_t Exponent,
+                                                   unsigned &Alignment) {
+  // Note: Alignment in bitcode files is incremented by 1, so that zero
+  // can be used for default alignment.
+  if (Exponent > Value::MaxAlignmentExponent + 1)
+    return Error("Invalid alignment value");
+  Alignment = (1 << static_cast<unsigned>(Exponent)) >> 1;
+  return std::error_code();
+}
+
 std::error_code BitcodeReader::ParseAttrKind(uint64_t Code,
                                              Attribute::AttrKind *Kind) {
   *Kind = GetAttrFromCode(Code);
@@ -2462,7 +2472,9 @@ std::error_code BitcodeReader::ParseModule(bool Resume) {
       bool isConstant = Record[1];
       uint64_t RawLinkage = Record[3];
       GlobalValue::LinkageTypes Linkage = getDecodedLinkage(RawLinkage);
-      unsigned Alignment = (1 << Record[4]) >> 1;
+      unsigned Alignment;
+      if (std::error_code EC = parseAlignmentValue(Record[4], Alignment))
+        return EC;
       std::string Section;
       if (Record[5]) {
         if (Record[5]-1 >= SectionTable.size())
@@ -2542,7 +2554,10 @@ std::error_code BitcodeReader::ParseModule(bool Resume) {
       Func->setLinkage(getDecodedLinkage(RawLinkage));
       Func->setAttributes(getAttributes(Record[4]));
 
-      Func->setAlignment((1 << Record[5]) >> 1);
+      unsigned Alignment;
+      if (std::error_code EC = parseAlignmentValue(Record[5], Alignment))
+        return EC;
+      Func->setAlignment(Alignment);
       if (Record[6]) {
         if (Record[6]-1 >= SectionTable.size())
           return Error("Invalid ID");
@@ -3539,12 +3554,17 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
         dyn_cast_or_null<PointerType>(getTypeByID(Record[0]));
       Type *OpTy = getTypeByID(Record[1]);
       Value *Size = getFnValueByID(Record[2], OpTy);
-      unsigned AlignRecord = Record[3];
-      bool InAlloca = AlignRecord & (1 << 5);
-      unsigned Align = AlignRecord & ((1 << 5) - 1);
+      uint64_t AlignRecord = Record[3];
+      const uint64_t InAllocaMask = uint64_t(1) << 5;
+      bool InAlloca = AlignRecord & InAllocaMask;
+      unsigned Align;
+      if (std::error_code EC =
+          parseAlignmentValue(AlignRecord & ~InAllocaMask, Align)) {
+        return EC;
+      }
       if (!Ty || !Size)
         return Error("Invalid record");
-      AllocaInst *AI = new AllocaInst(Ty->getElementType(), Size, (1 << Align) >> 1);
+      AllocaInst *AI = new AllocaInst(Ty->getElementType(), Size, Align);
       AI->setUsedWithInAlloca(InAlloca);
       I = AI;
       InstructionList.push_back(I);
@@ -3556,8 +3576,10 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
       if (getValueTypePair(Record, OpNum, NextValueNo, Op) ||
           OpNum+2 != Record.size())
         return Error("Invalid record");
-
-      I = new LoadInst(Op, "", Record[OpNum+1], (1 << Record[OpNum]) >> 1);
+      unsigned Align;
+      if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
+        return EC;
+      I = new LoadInst(Op, "", Record[OpNum+1], Align);
       InstructionList.push_back(I);
       break;
     }
@@ -3577,8 +3599,10 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
         return Error("Invalid record");
       SynchronizationScope SynchScope = GetDecodedSynchScope(Record[OpNum+3]);
 
-      I = new LoadInst(Op, "", Record[OpNum+1], (1 << Record[OpNum]) >> 1,
-                       Ordering, SynchScope);
+      unsigned Align;
+      if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
+        return EC;
+      I = new LoadInst(Op, "", Record[OpNum+1], Align, Ordering, SynchScope);
       InstructionList.push_back(I);
       break;
     }
@@ -3590,8 +3614,10 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
                     cast<PointerType>(Ptr->getType())->getElementType(), Val) ||
           OpNum+2 != Record.size())
         return Error("Invalid record");
-
-      I = new StoreInst(Val, Ptr, Record[OpNum+1], (1 << Record[OpNum]) >> 1);
+      unsigned Align;
+      if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
+        return EC;
+      I = new StoreInst(Val, Ptr, Record[OpNum+1], Align);
       InstructionList.push_back(I);
       break;
     }
@@ -3613,8 +3639,10 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
       if (Ordering != NotAtomic && Record[OpNum] == 0)
         return Error("Invalid record");
 
-      I = new StoreInst(Val, Ptr, Record[OpNum+1], (1 << Record[OpNum]) >> 1,
-                        Ordering, SynchScope);
+      unsigned Align;
+      if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
+        return EC;
+      I = new StoreInst(Val, Ptr, Record[OpNum+1], Align, Ordering, SynchScope);
       InstructionList.push_back(I);
       break;
     }
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.h b/llvm/lib/Bitcode/Reader/BitcodeReader.h
index 5090be48450..9803e78b929 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.h
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.h
@@ -335,6 +335,10 @@ private:
     return getFnValueByID(ValNo, Ty);
   }
 
+  /// Converts alignment exponent (i.e. power of two (or zero)) to the
+  /// corresponding alignment to use. If alignment is too large, returns
+  /// a corresponding error code.
+  std::error_code parseAlignmentValue(uint64_t Exponent, unsigned &Alignment);
   std::error_code ParseAttrKind(uint64_t Code, Attribute::AttrKind *Kind);
   std::error_code ParseModule(bool Resume);
   std::error_code ParseAttributeBlock();