[analyzer] Check NULL pointer dereference issue for memset function

Reviewers: dcoughlin, zaks.anna, NoQ, danielmarjamaki

Reviewed By: NoQ, danielmarjamaki

Differential Revision: https://reviews.llvm.org/D31868

llvm-svn: 305773

1 files changed, 51 insertions, 0 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
index 32e3ce9270a..77c24629d71 100644
--- a/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
@@ -120,6 +120,7 @@ public:
   void evalStdCopy(CheckerContext &C, const CallExpr *CE) const;
   void evalStdCopyBackward(CheckerContext &C, const CallExpr *CE) const;
   void evalStdCopyCommon(CheckerContext &C, const CallExpr *CE) const;
+  void evalMemset(CheckerContext &C, const CallExpr *CE) const;
 
   // Utility methods
   std::pair<ProgramStateRef , ProgramStateRef >
@@ -1999,6 +2000,54 @@ void CStringChecker::evalStdCopyCommon(CheckerContext &C,
   C.addTransition(State);
 }
 
+void CStringChecker::evalMemset(CheckerContext &C, const CallExpr *CE) const {
+  if (CE->getNumArgs() != 3)
+    return;
+
+  CurrentFunctionDescription = "memory set function";
+
+  const Expr *Mem = CE->getArg(0);
+  const Expr *Size = CE->getArg(2);
+  ProgramStateRef State = C.getState();
+
+  // See if the size argument is zero.
+  const LocationContext *LCtx = C.getLocationContext();
+  SVal SizeVal = State->getSVal(Size, LCtx);
+  QualType SizeTy = Size->getType();
+
+  ProgramStateRef StateZeroSize, StateNonZeroSize;
+  std::tie(StateZeroSize, StateNonZeroSize) =
+    assumeZero(C, State, SizeVal, SizeTy);
+
+  // Get the value of the memory area.
+  SVal MemVal = State->getSVal(Mem, LCtx);
+
+  // If the size is zero, there won't be any actual memory access, so
+  // just bind the return value to the Mem buffer and return.
+  if (StateZeroSize && !StateNonZeroSize) {
+    StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, MemVal);
+    C.addTransition(StateZeroSize);
+    return;
+  }
+
+  // Ensure the memory area is not null.
+  // If it is NULL there will be a NULL pointer dereference.
+  State = checkNonNull(C, StateNonZeroSize, Mem, MemVal);
+  if (!State)
+    return;
+
+  State = CheckBufferAccess(C, State, Size, Mem);
+  if (!State)
+    return;
+  State = InvalidateBuffer(C, State, Mem, C.getSVal(Mem),
+                           /*IsSourceBuffer*/false, Size);
+  if (!State)
+    return;
+
+  State = State->BindExpr(CE, LCtx, MemVal);
+  C.addTransition(State);
+}
+
 static bool isCPPStdLibraryFunction(const FunctionDecl *FD, StringRef Name) {
   IdentifierInfo *II = FD->getIdentifier();
   if (!II)
@@ -2032,6 +2081,8 @@ bool CStringChecker::evalCall(const CallExpr *CE, CheckerContext &C) const {
     evalFunction =  &CStringChecker::evalMemcmp;
   else if (C.isCLibraryFunction(FDecl, "memmove"))
     evalFunction =  &CStringChecker::evalMemmove;
+  else if (C.isCLibraryFunction(FDecl, "memset"))
+    evalFunction =  &CStringChecker::evalMemset;
   else if (C.isCLibraryFunction(FDecl, "strcpy"))
     evalFunction =  &CStringChecker::evalStrcpy;
   else if (C.isCLibraryFunction(FDecl, "strncpy"))