Add checker for CWE-469: Use of Pointer Subtraction to Determine Size. This

checker does not build sink nodes. Because svaluator computes an unknown value
for the subtraction now.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@86517 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/GRExprEngineInternalChecks.cpp

@@ -412,6 +412,7 @@ void GRExprEngine::RegisterInternalChecks() {
   RegisterDivZeroChecker(*this);
   RegisterReturnStackAddressChecker(*this);
   RegisterReturnUndefChecker(*this);
+  RegisterPointerSubChecker(*this);
 
   // Note that this must be registered after ReturnStackAddressChecker.
   RegisterReturnPointerRangeChecker(*this);

lib/Analysis/GRExprEngineInternalChecks.h

@@ -24,6 +24,6 @@ void RegisterReturnPointerRangeChecker(GRExprEngine &Eng);
 void RegisterReturnStackAddressChecker(GRExprEngine &Eng);  
 void RegisterReturnUndefChecker(GRExprEngine &Eng);
 void RegisterVLASizeChecker(GRExprEngine &Eng);
-  
+void RegisterPointerSubChecker(GRExprEngine &Eng);  
 } // end clang namespace
 #endif

lib/Analysis/PointerSubChecker.cpp

@@ -0,0 +1,71 @@
+//=== PointerSubChecker.cpp - Pointer subtraction checker ------*- C++ -*--===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This files defines PointerSubChecker, a builtin checker that checks for
+// pointer subtractions on two pointers pointing to different memory chunks. 
+// This check corresponds to CWE-469.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/PathSensitive/CheckerVisitor.h"
+#include "GRExprEngineInternalChecks.h"
+
+using namespace clang;
+
+namespace {
+class VISIBILITY_HIDDEN PointerSubChecker 
+  : public CheckerVisitor<PointerSubChecker> {
+  BuiltinBug *BT;
+public:
+  PointerSubChecker() : BT(0) {}
+  static void *getTag();
+  void PreVisitBinaryOperator(CheckerContext &C, const BinaryOperator *B);
+};
+}
+
+void *PointerSubChecker::getTag() {
+  static int x;
+  return &x;
+}
+
+void PointerSubChecker::PreVisitBinaryOperator(CheckerContext &C,
+                                               const BinaryOperator *B) {
+  // When doing pointer subtraction, if the two pointers do not point to the
+  // same memory chunk, emit a warning.
+  if (B->getOpcode() != BinaryOperator::Sub)
+    return;
+
+  const GRState *state = C.getState();
+  SVal LV = state->getSVal(B->getLHS());
+  SVal RV = state->getSVal(B->getRHS());
+
+  const MemRegion *LR = LV.getAsRegion();
+  const MemRegion *RR = RV.getAsRegion();
+
+  if (!(LR && RR) || (LR == RR))
+    return;
+
+  // We don't reason about SymbolicRegions for now.
+  if (isa<SymbolicRegion>(LR) || isa<SymbolicRegion>(RR))
+    return;
+
+  if (ExplodedNode *N = C.GenerateNode(B)) {
+    if (!BT)
+      BT = new BuiltinBug("Pointer subtraction", 
+                          "Subtraction of two pointers that do not point to the same memory chunk may cause incorrect result.");
+    RangedBugReport *R = new RangedBugReport(*BT, BT->getDescription().c_str(),
+                                             N);
+    R->addRange(B->getSourceRange());
+    C.EmitReport(R);
+  }
+}
+
+void clang::RegisterPointerSubChecker(GRExprEngine &Eng) {
+  Eng.registerCheck(new PointerSubChecker());
+}

test/Analysis/ptr-arith.c

@@ -31,3 +31,8 @@ domain_port (const char *domain_b, const char *domain_e,
     port = 10 * port + (*p - '0');
   return port;
 }
+
+void f3() {
+  int x, y;
+  int d = &y - &x; // expected-warning{{Subtraction of two pointers that do not point to the same memory chunk may cause incorrect result.}}
+}