[clang/asan] call __asan_poison_cxx_array_cookie after operator new[]

Summary:
PR19838
When operator new[] is called and an array cookie is created
we want asan to detect buffer overflow bugs that touch the cookie.
For that we need to
  a) poison the shadow for the array cookie (call __asan_poison_cxx_array_cookie).
  b) ignore the legal accesses to the cookie generated by clang (add 'nosanitize' metadata)

Reviewers: timurrrr, samsonov, rsmith

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4774

llvm-svn: 216434

clang/lib/CodeGen/CodeGenFunction.cpp

@@ -1683,11 +1683,8 @@ void CodeGenFunction::InsertHelper(llvm::Instruction *I,
                                    llvm::BasicBlock *BB,
                                    llvm::BasicBlock::iterator InsertPt) const {
   LoopStack.InsertHelper(I);
-  if (IsSanitizerScope) {
-    I->setMetadata(
-        CGM.getModule().getMDKindID("nosanitize"),
-        llvm::MDNode::get(CGM.getLLVMContext(), ArrayRef<llvm::Value *>()));
-  }
+  if (IsSanitizerScope)
+    CGM.getSanitizerMetadata()->disableSanitizerForInstruction(I);
 }
 
 template <bool PreserveNames>

clang/lib/CodeGen/ItaniumCXXABI.cpp

@@ -1472,10 +1472,19 @@ llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
                                                  CookieOffset.getQuantity());
 
   // Write the number of elements into the appropriate slot.
-  llvm::Value *NumElementsPtr
-    = CGF.Builder.CreateBitCast(CookiePtr,
-                                CGF.ConvertType(SizeTy)->getPointerTo(AS));
-  CGF.Builder.CreateStore(NumElements, NumElementsPtr);
+  llvm::Type *NumElementsTy = CGF.ConvertType(SizeTy)->getPointerTo(AS);
+  llvm::Value *NumElementsPtr =
+      CGF.Builder.CreateBitCast(CookiePtr, NumElementsTy);
+  llvm::Instruction *SI = CGF.Builder.CreateStore(NumElements, NumElementsPtr);
+  if (CGM.getLangOpts().Sanitize.Address &&
+      expr->getOperatorNew()->isReplaceableGlobalAllocationFunction()) {
+    CGM.getSanitizerMetadata()->disableSanitizerForInstruction(SI);
+    llvm::FunctionType *FTy =
+        llvm::FunctionType::get(CGM.VoidTy, NumElementsTy, false);
+    llvm::Constant *F =
+        CGM.CreateRuntimeFunction(FTy, "__asan_poison_cxx_array_cookie");
+    CGF.Builder.CreateCall(F, NumElementsPtr);
+  }
 
   // Finally, compute a pointer to the actual data buffer by skipping
   // over the cookie completely.
@@ -1498,7 +1507,10 @@ llvm::Value *ItaniumCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
   unsigned AS = allocPtr->getType()->getPointerAddressSpace();
   numElementsPtr = 
     CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
-  return CGF.Builder.CreateLoad(numElementsPtr);
+  llvm::Instruction *LI = CGF.Builder.CreateLoad(numElementsPtr);
+  if (CGM.getLangOpts().Sanitize.Address)
+    CGM.getSanitizerMetadata()->disableSanitizerForInstruction(LI);
+  return LI;
 }
 
 CharUnits ARMCXXABI::getArrayCookieSizeImpl(QualType elementType) {

clang/lib/CodeGen/SanitizerMetadata.cpp

@@ -67,6 +67,12 @@ void SanitizerMetadata::disableSanitizerForGlobal(llvm::GlobalVariable *GV) {
     reportGlobalToASan(GV, SourceLocation(), "", false, true);
 }
 
+void SanitizerMetadata::disableSanitizerForInstruction(llvm::Instruction *I) {
+  I->setMetadata(
+      CGM.getModule().getMDKindID("nosanitize"),
+      llvm::MDNode::get(CGM.getLLVMContext(), ArrayRef<llvm::Value *>()));
+}
+
 llvm::MDNode *SanitizerMetadata::getLocationMetadata(SourceLocation Loc) {
   PresumedLoc PLoc = CGM.getContext().getSourceManager().getPresumedLoc(Loc);
   if (!PLoc.isValid())

clang/lib/CodeGen/SanitizerMetadata.h

@@ -18,6 +18,7 @@
 
 namespace llvm {
 class GlobalVariable;
+class Instruction;
 class MDNode;
 }
 
@@ -41,6 +42,7 @@ class SanitizerMetadata {
                           StringRef Name, bool IsDynInit = false,
                           bool IsBlacklisted = false);
   void disableSanitizerForGlobal(llvm::GlobalVariable *GV);
+  void disableSanitizerForInstruction(llvm::Instruction *I);
 private:
   llvm::MDNode *getLocationMetadata(SourceLocation Loc);
 };

clang/test/CodeGen/address-sanitizer-and-array-cookie.cpp

@@ -0,0 +1,54 @@
+// RUN: %clang_cc1 -triple x86_64-gnu-linux -emit-llvm -o - %s | FileCheck %s -check-prefix=PLAIN
+// RUN: %clang_cc1 -triple x86_64-gnu-linux -emit-llvm -o - -fsanitize=address %s | FileCheck %s -check-prefix=ASAN
+
+typedef __typeof__(sizeof(0)) size_t;
+namespace std {
+  struct nothrow_t {};
+  std::nothrow_t nothrow;
+}
+void *operator new[](size_t, const std::nothrow_t &) throw();
+void *operator new[](size_t, char *);
+
+struct C {
+  int x;
+  ~C();
+};
+
+C *CallNew() {
+  return new C[10];
+}
+// PLAIN-LABEL: CallNew
+// PLAIN-NOT: nosanitize
+// PLAIN-NOT: __asan_poison_cxx_array_cookie
+// ASAN-LABEL: CallNew
+// ASAN: store{{.*}}nosanitize
+// ASAN-NOT: nosanitize
+// ASAN: call void @__asan_poison_cxx_array_cookie
+
+C *CallNewNoThrow() {
+  return new (std::nothrow) C[10];
+}
+// PLAIN-LABEL: CallNewNoThrow
+// PLAIN-NOT: nosanitize
+// PLAIN-NOT: __asan_poison_cxx_array_cookie
+// ASAN-LABEL: CallNewNoThrow
+// ASAN: store{{.*}}nosanitize
+// ASAN-NOT: nosanitize
+// ASAN: call void @__asan_poison_cxx_array_cookie
+
+void CallDelete(C *c) {
+  delete [] c;
+}
+
+// PLAIN-LABEL: CallDelete
+// PLAIN-NOT: nosanitize
+// ASAN-LABEL: CallDelete
+// ASAN: load{{.*}}!nosanitize
+// ASAN-NOT: nosanitize
+
+char Buffer[20];
+C *CallPlacementNew() {
+  return new (Buffer) C[20];
+}
+// ASAN-LABEL: CallPlacementNew
+// ASAN-NOT: __asan_poison_cxx_array_cookie