devnexen created this revision.
devnexen added reviewers: dcoughlin, dergachev.a.
devnexen created this object with visibility "All Users".
Herald added subscribers: cfe-commits, hintonda, mgorny.
This new checker tests if both PROT_WRITE and PROT_EXEC have been set.
Repository:
rC Clang
https://reviews.llvm.org/D42645
Files:
include/clang/StaticAnalyzer/Checkers/Checkers.td
lib/StaticAnalyzer/Checkers/CMakeLists.txt
lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
Index: lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
+++ lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp
@@ -0,0 +1,76 @@
+// 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 detects a common memory allocation security flaw.
+// Suppose 'unsigned int n' comes from an untrusted source. If the
+// code looks like 'malloc (n * 4)', and an attacker can make 'n' be
+// say MAX_UINT/4+2, then instead of allocating the correct 'n' 4-byte
+// elements, this will actually allocate only two because of overflow.
+// Then when the rest of the program attempts to store values past the
+// second element, these values will actually overwrite other items in
+// the heap, probably allowing the attacker to execute arbitrary code.
+//
+//===----------------------------------------------------------------------===//
+
+#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/CheckerContext.h"
+
+using namespace clang;
+using namespace ento;
+using llvm::APSInt;
+
+namespace {
+class MmapWriteExecChecker : public Checker<check::PostStmt<CallExpr>> {
+#ifdef __GLIBC__
+ static const int ProtWrite = 0x02;
+ static const int ProtExec = 0x01;
+#else
+ static const int ProtWrite = 0x02;
+ static const int ProtExec = 0x04;
+#endif
+ mutable std::unique_ptr<BugType> BT;
+public:
+ void checkPostStmt(const CallExpr *S, CheckerContext &C) const;
+};
+}
+
+void MmapWriteExecChecker::checkPostStmt(const CallExpr *CE,
+ CheckerContext &C) const {
+ StringRef FName = C.getCalleeName(CE);
+ if (FName.empty())
+ return;
+
+ if (FName == "mmap") {
+ SVal ProtVal = C.getSVal(CE->getArg(2));
+ Optional<nonloc::ConcreteInt> Prot = ProtVal.getAs<nonloc::ConcreteInt>();
+ int64_t prot = Prot->getValue().getSExtValue();
+
+ if ((prot & (ProtWrite | ProtExec))) {
+ if (!BT) {
+ BT.reset(new BugType(this, "W^X check fail", "Write Exec prot flags set"));
+ ExplodedNode *N = C.generateErrorNode();
+ if (!N)
+ return;
+
+ auto Report = llvm::make_unique<BugReport>(
+ *BT, "Both PROT_WRITE and PROT_EXEC flags had been set", N);
+ Report->addRange(CE->getArg(2)->getSourceRange());
+ C.emitReport(std::move(Report));
+ }
+ }
+ }
+}
+
+void ento::registerMmapWriteExecChecker(CheckerManager &mgr) {
+ mgr.registerChecker<MmapWriteExecChecker>();
+}
Index: lib/StaticAnalyzer/Checkers/CMakeLists.txt
===================================================================
--- lib/StaticAnalyzer/Checkers/CMakeLists.txt
+++ lib/StaticAnalyzer/Checkers/CMakeLists.txt
@@ -50,6 +50,7 @@
MallocOverflowSecurityChecker.cpp
MallocSizeofChecker.cpp
MisusedMovedObjectChecker.cpp
+ MmapWriteExecChecker.cpp
MPI-Checker/MPIBugReporter.cpp
MPI-Checker/MPIChecker.cpp
MPI-Checker/MPIFunctionClassifier.cpp
Index: include/clang/StaticAnalyzer/Checkers/Checkers.td
===================================================================
--- include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -86,7 +86,7 @@
// The APIModeling package is for checkers that model APIs and don't perform
// any diagnostics. These checkers are always turned on; this package is
-// intended for API modeling that is not controlled by the the target triple.
+// intended for API modeling that is not controlled by the target triple.
def APIModeling : Package<"apiModeling">, Hidden;
def GoogleAPIModeling : Package<"google">, InPackage<APIModeling>;
@@ -414,6 +414,10 @@
HelpText<"Check for overflows in the arguments to malloc()">,
DescFile<"MallocOverflowSecurityChecker.cpp">;
+def MmapWriteExecChecker : Checker<"MmapWriteExecChecker">,
+ HelpText<"Check if mmap() call is not both writable and executable">,
+ DescFile<"MmapWriteExecChecker.cpp">;
+
} // end "alpha.security"
//===----------------------------------------------------------------------===//
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