1 files changed, 88 insertions, 0 deletions
diff --git a/lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp b/lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
new file mode 100644
index 000000000000..5060b0e0a6e0
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+++ b/lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
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+// MmapWriteExecChecker.cpp - Check for the prot argument -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This checker tests the 3rd argument of mmap's calls to check if
+// it is writable and executable in the same time. It's somehow
+// an optional checker since for example in JIT libraries it is pretty common.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ClangSACheckers.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/CallEvent.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+
+using namespace clang;
+using namespace ento;
+using llvm::APSInt;
+
+namespace {
+class MmapWriteExecChecker : public Checker<check::PreCall> {
+  CallDescription MmapFn;
+  CallDescription MprotectFn;
+  static int ProtWrite;
+  static int ProtExec;
+  static int ProtRead;
+  mutable std::unique_ptr<BugType> BT;
+public:
+  MmapWriteExecChecker() : MmapFn("mmap", 6), MprotectFn("mprotect", 3) {}
+  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
+  int ProtExecOv;
+  int ProtReadOv;
+};
+}
+
+int MmapWriteExecChecker::ProtWrite = 0x02;
+int MmapWriteExecChecker::ProtExec  = 0x04;
+int MmapWriteExecChecker::ProtRead  = 0x01;
+
+void MmapWriteExecChecker::checkPreCall(const CallEvent &Call,
+                                         CheckerContext &C) const {
+  if (Call.isCalled(MmapFn) || Call.isCalled(MprotectFn)) {
+    SVal ProtVal = Call.getArgSVal(2);
+    Optional<nonloc::ConcreteInt> ProtLoc = ProtVal.getAs<nonloc::ConcreteInt>();
+    int64_t Prot = ProtLoc->getValue().getSExtValue();
+    if (ProtExecOv != ProtExec)
+      ProtExec = ProtExecOv;
+    if (ProtReadOv != ProtRead)
+      ProtRead = ProtReadOv;
+
+    // Wrong settings
+    if (ProtRead == ProtExec)
+      return;
+
+    if ((Prot & (ProtWrite | ProtExec)) == (ProtWrite | ProtExec)) {
+      if (!BT)
+        BT.reset(new BugType(this, "W^X check fails, Write Exec prot flags set", "Security"));
+
+      ExplodedNode *N = C.generateNonFatalErrorNode();
+      if (!N)
+        return;
+
+      auto Report = llvm::make_unique<BugReport>(
+          *BT, "Both PROT_WRITE and PROT_EXEC flags are set. This can "
+               "lead to exploitable memory regions, which could be overwritten "
+               "with malicious code", N);
+      Report->addRange(Call.getArgSourceRange(2));
+      C.emitReport(std::move(Report));
+    }
+  }
+}
+
+void ento::registerMmapWriteExecChecker(CheckerManager &mgr) {
+  MmapWriteExecChecker *Mwec =
+      mgr.registerChecker<MmapWriteExecChecker>();
+  Mwec->ProtExecOv =
+    mgr.getAnalyzerOptions().getOptionAsInteger("MmapProtExec", 0x04, Mwec);
+  Mwec->ProtReadOv =
+    mgr.getAnalyzerOptions().getOptionAsInteger("MmapProtRead", 0x01, Mwec);
+}