1 files changed, 79 insertions, 0 deletions
diff --git a/clang/lib/StaticAnalyzer/Checkers/PointerSubChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/PointerSubChecker.cpp
new file mode 100644
index 0000000000000..88d0eb2ae7484
--- /dev/null
+++ b/clang/lib/StaticAnalyzer/Checkers/PointerSubChecker.cpp
@@ -0,0 +1,79 @@
+//=== PointerSubChecker.cpp - Pointer subtraction checker ------*- C++ -*--===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// 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/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/CheckerManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class PointerSubChecker
+  : public Checker< check::PreStmt<BinaryOperator> > {
+  mutable std::unique_ptr<BuiltinBug> BT;
+
+public:
+  void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
+};
+}
+
+void PointerSubChecker::checkPreStmt(const BinaryOperator *B,
+                                     CheckerContext &C) const {
+  // When doing pointer subtraction, if the two pointers do not point to the
+  // same memory chunk, emit a warning.
+  if (B->getOpcode() != BO_Sub)
+    return;
+
+  SVal LV = C.getSVal(B->getLHS());
+  SVal RV = C.getSVal(B->getRHS());
+
+  const MemRegion *LR = LV.getAsRegion();
+  const MemRegion *RR = RV.getAsRegion();
+
+  if (!(LR && RR))
+    return;
+
+  const MemRegion *BaseLR = LR->getBaseRegion();
+  const MemRegion *BaseRR = RR->getBaseRegion();
+
+  if (BaseLR == BaseRR)
+    return;
+
+  // Allow arithmetic on different symbolic regions.
+  if (isa<SymbolicRegion>(BaseLR) || isa<SymbolicRegion>(BaseRR))
+    return;
+
+  if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
+    if (!BT)
+      BT.reset(
+          new BuiltinBug(this, "Pointer subtraction",
+                         "Subtraction of two pointers that do not point to "
+                         "the same memory chunk may cause incorrect result."));
+    auto R =
+        std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N);
+    R->addRange(B->getSourceRange());
+    C.emitReport(std::move(R));
+  }
+}
+
+void ento::registerPointerSubChecker(CheckerManager &mgr) {
+  mgr.registerChecker<PointerSubChecker>();
+}
+
+bool ento::shouldRegisterPointerSubChecker(const LangOptions &LO) {
+  return true;
+}