[analyzer] Make VLA checker taint aware.

Also, slightly modify the diagnostic message in ArrayBound and DivZero (still use 'taint', which might not mean much to the user, but plan on changing it later).

llvm-svn: 148626

clang/lib/StaticAnalyzer/Checkers/ArrayBoundCheckerV2.cpp

@@ -28,7 +28,7 @@ class ArrayBoundCheckerV2 :
     public Checker<check::Location> {
   mutable llvm::OwningPtr<BuiltinBug> BT;
       
-  enum OOB_Kind { OOB_Precedes, OOB_Excedes };
+  enum OOB_Kind { OOB_Precedes, OOB_Excedes, OOB_Tainted };
   
   void reportOOB(CheckerContext &C, const ProgramState *errorState,
                  OOB_Kind kind) const;
@@ -157,7 +157,7 @@ void ArrayBoundCheckerV2::checkLocation(SVal location, bool isLoad,
     // If we are under constrained and the index variables are tainted, report.
     if (state_exceedsUpperBound && state_withinUpperBound) {
       if (state->isTainted(rawOffset.getByteOffset()))
-        reportOOB(checkerContext, state_exceedsUpperBound, OOB_Excedes);
+        reportOOB(checkerContext, state_exceedsUpperBound, OOB_Tainted);
         return;
     }
   
@@ -193,9 +193,18 @@ void ArrayBoundCheckerV2::reportOOB(CheckerContext &checkerContext,
 
   llvm::SmallString<256> buf;
   llvm::raw_svector_ostream os(buf);
-  os << "Out of bound memory access "
-     << (kind == OOB_Precedes ? "(accessed memory precedes memory block)"
-                              : "(access exceeds upper limit of memory block)");
+  os << "Out of bound memory access ";
+  switch (kind) {
+  case OOB_Precedes:
+    os << "(accessed memory precedes memory block)";
+    break;
+  case OOB_Excedes:
+    os << "(access exceeds upper limit of memory block)";
+    break;
+  case OOB_Tainted:
+    os << "(index is tainted)";
+    break;
+  }
 
   checkerContext.EmitReport(new BugReport(*BT, os.str(), errorNode));
 }

clang/lib/StaticAnalyzer/Checkers/DivZeroChecker.cpp

@@ -37,10 +37,10 @@ void DivZeroChecker::reportBug(const char *Msg,
                                CheckerContext &C) const {
   if (ExplodedNode *N = C.generateSink(StateZero)) {
     if (!BT)
-      BT.reset(new BuiltinBug(Msg));
+      BT.reset(new BuiltinBug("Division by zero"));
 
     BugReport *R =
-      new BugReport(*BT, BT->getDescription(), N);
+      new BugReport(*BT, Msg, N);
 
     R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
                                  bugreporter::GetDenomExpr(N)));

clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp

@@ -26,14 +26,52 @@ using namespace ento;
 
 namespace {
 class VLASizeChecker : public Checker< check::PreStmt<DeclStmt> > {
-  mutable llvm::OwningPtr<BugType> BT_zero;
-  mutable llvm::OwningPtr<BugType> BT_undef;
-  
+  mutable llvm::OwningPtr<BugType> BT;
+  enum VLASize_Kind { VLA_Garbage, VLA_Zero, VLA_Tainted };
+
+  void reportBug(VLASize_Kind Kind,
+                 const Expr *SizeE,
+                 const ProgramState *State,
+                 CheckerContext &C) const;
 public:
   void checkPreStmt(const DeclStmt *DS, CheckerContext &C) const;
 };
 } // end anonymous namespace
 
+void VLASizeChecker::reportBug(VLASize_Kind Kind,
+                               const Expr *SizeE,
+                               const ProgramState *State,
+                               CheckerContext &C) const {
+  // Generate an error node.
+  ExplodedNode *N = C.generateSink(State);
+  if (!N)
+    return;
+
+  if (!BT)
+    BT.reset(new BuiltinBug("Dangerous variable-length array (VLA) declaration"));
+
+  llvm::SmallString<256> buf;
+  llvm::raw_svector_ostream os(buf);
+  os << "Declared variable-length array (VLA) ";
+  switch (Kind) {
+  case VLA_Garbage:
+    os << "uses a garbage value as its size";
+    break;
+  case VLA_Zero:
+    os << "has zero size";
+    break;
+  case VLA_Tainted:
+    os << "has tainted size";
+    break;
+  }
+
+  BugReport *report = new BugReport(*BT, os.str(), N);
+  report->addRange(SizeE->getSourceRange());
+  report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, SizeE));
+  C.EmitReport(report);
+  return;
+}
+
 void VLASizeChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const {
   if (!DS->isSingleDecl())
     return;
@@ -53,20 +91,7 @@ void VLASizeChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const {
   SVal sizeV = state->getSVal(SE, C.getLocationContext());
 
   if (sizeV.isUndef()) {
-    // Generate an error node.
-    ExplodedNode *N = C.generateSink();
-    if (!N)
-      return;
-    
-    if (!BT_undef)
-      BT_undef.reset(new BuiltinBug("Declared variable-length array (VLA) "
-                                    "uses a garbage value as its size"));
-
-    BugReport *report =
-      new BugReport(*BT_undef, BT_undef->getName(), N);
-    report->addRange(SE->getSourceRange());
-    report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, SE));
-    C.EmitReport(report);
+    reportBug(VLA_Garbage, SE, state, C);
     return;
   }
 
@@ -75,6 +100,12 @@ void VLASizeChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const {
   if (sizeV.isUnknown())
     return;
   
+  // Check if the size is tainted.
+  if (state->isTainted(sizeV)) {
+    reportBug(VLA_Tainted, SE, 0, C);
+    return;
+  }
+
   // Check if the size is zero.
   DefinedSVal sizeD = cast<DefinedSVal>(sizeV);
 
@@ -82,16 +113,7 @@ void VLASizeChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const {
   llvm::tie(stateNotZero, stateZero) = state->assume(sizeD);
 
   if (stateZero && !stateNotZero) {
-    ExplodedNode *N = C.generateSink(stateZero);
-    if (!BT_zero)
-      BT_zero.reset(new BuiltinBug("Declared variable-length array (VLA) has "
-                                   "zero size"));
-
-    BugReport *report =
-      new BugReport(*BT_zero, BT_zero->getName(), N);
-    report->addRange(SE->getSourceRange());
-    report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, SE));
-    C.EmitReport(report);
+    reportBug(VLA_Zero, SE, stateZero, C);
     return;
   }
  

clang/test/Analysis/taint-generic.c

@@ -70,7 +70,7 @@ void scanfArg() {
 
 void bufferGetchar(int x) {
   int m = getchar();
-  Buffer[m] = 1;  //expected-warning {{Out of bound memory access }}
+  Buffer[m] = 1;  //expected-warning {{Out of bound memory access (index is tainted)}}
 }
 
 void testUncontrolledFormatString(char **p) {
@@ -176,3 +176,10 @@ int testDivByZero() {
   scanf("%d", &x);
   return 5/x; // expected-warning {{Division by a tainted value, possibly zero}}
 }
+
+// Zero-sized VLAs.
+void testTaintedVLASize() {
+  int x;
+  scanf("%d", &x);
+  int vla[x]; // expected-warning{{Declared variable-length array (VLA) has tainted size}}
+}