| //= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- C++ -*-// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This defines UnixAPIChecker, which is an assortment of checks on calls |
| // to various, widely used UNIX/Posix functions. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "ClangSACheckers.h" |
| #include "clang/StaticAnalyzer/Core/Checker.h" |
| #include "clang/StaticAnalyzer/Core/CheckerManager.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" |
| #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" |
| #include "clang/Basic/TargetInfo.h" |
| #include "llvm/ADT/Optional.h" |
| #include "llvm/ADT/SmallString.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/StringSwitch.h" |
| #include <fcntl.h> |
| |
| using namespace clang; |
| using namespace ento; |
| using llvm::Optional; |
| |
| namespace { |
| class UnixAPIChecker : public Checker< check::PreStmt<CallExpr> > { |
| mutable OwningPtr<BugType> BT_open, BT_pthreadOnce, BT_mallocZero; |
| mutable Optional<uint64_t> Val_O_CREAT; |
| |
| public: |
| void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; |
| |
| void CheckOpen(CheckerContext &C, const CallExpr *CE) const; |
| void CheckPthreadOnce(CheckerContext &C, const CallExpr *CE) const; |
| void CheckCallocZero(CheckerContext &C, const CallExpr *CE) const; |
| void CheckMallocZero(CheckerContext &C, const CallExpr *CE) const; |
| void CheckReallocZero(CheckerContext &C, const CallExpr *CE) const; |
| void CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const; |
| void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const; |
| |
| typedef void (UnixAPIChecker::*SubChecker)(CheckerContext &, |
| const CallExpr *) const; |
| private: |
| bool ReportZeroByteAllocation(CheckerContext &C, |
| ProgramStateRef falseState, |
| const Expr *arg, |
| const char *fn_name) const; |
| void BasicAllocationCheck(CheckerContext &C, |
| const CallExpr *CE, |
| const unsigned numArgs, |
| const unsigned sizeArg, |
| const char *fn) const; |
| }; |
| } //end anonymous namespace |
| |
| //===----------------------------------------------------------------------===// |
| // Utility functions. |
| //===----------------------------------------------------------------------===// |
| |
| static inline void LazyInitialize(OwningPtr<BugType> &BT, |
| const char *name) { |
| if (BT) |
| return; |
| BT.reset(new BugType(name, "Unix API")); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // "open" (man 2 open) |
| //===----------------------------------------------------------------------===// |
| |
| void UnixAPIChecker::CheckOpen(CheckerContext &C, const CallExpr *CE) const { |
| // The definition of O_CREAT is platform specific. We need a better way |
| // of querying this information from the checking environment. |
| if (!Val_O_CREAT.hasValue()) { |
| if (C.getASTContext().getTargetInfo().getTriple().getVendor() |
| == llvm::Triple::Apple) |
| Val_O_CREAT = 0x0200; |
| else { |
| // FIXME: We need a more general way of getting the O_CREAT value. |
| // We could possibly grovel through the preprocessor state, but |
| // that would require passing the Preprocessor object to the ExprEngine. |
| return; |
| } |
| } |
| |
| // Look at the 'oflags' argument for the O_CREAT flag. |
| ProgramStateRef state = C.getState(); |
| |
| if (CE->getNumArgs() < 2) { |
| // The frontend should issue a warning for this case, so this is a sanity |
| // check. |
| return; |
| } |
| |
| // Now check if oflags has O_CREAT set. |
| const Expr *oflagsEx = CE->getArg(1); |
| const SVal V = state->getSVal(oflagsEx, C.getLocationContext()); |
| if (!isa<NonLoc>(V)) { |
| // The case where 'V' can be a location can only be due to a bad header, |
| // so in this case bail out. |
| return; |
| } |
| NonLoc oflags = cast<NonLoc>(V); |
| NonLoc ocreateFlag = |
| cast<NonLoc>(C.getSValBuilder().makeIntVal(Val_O_CREAT.getValue(), |
| oflagsEx->getType())); |
| SVal maskedFlagsUC = C.getSValBuilder().evalBinOpNN(state, BO_And, |
| oflags, ocreateFlag, |
| oflagsEx->getType()); |
| if (maskedFlagsUC.isUnknownOrUndef()) |
| return; |
| DefinedSVal maskedFlags = cast<DefinedSVal>(maskedFlagsUC); |
| |
| // Check if maskedFlags is non-zero. |
| ProgramStateRef trueState, falseState; |
| llvm::tie(trueState, falseState) = state->assume(maskedFlags); |
| |
| // Only emit an error if the value of 'maskedFlags' is properly |
| // constrained; |
| if (!(trueState && !falseState)) |
| return; |
| |
| if (CE->getNumArgs() < 3) { |
| ExplodedNode *N = C.generateSink(trueState); |
| if (!N) |
| return; |
| |
| LazyInitialize(BT_open, "Improper use of 'open'"); |
| |
| BugReport *report = |
| new BugReport(*BT_open, |
| "Call to 'open' requires a third argument when " |
| "the 'O_CREAT' flag is set", N); |
| report->addRange(oflagsEx->getSourceRange()); |
| C.EmitReport(report); |
| } |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // pthread_once |
| //===----------------------------------------------------------------------===// |
| |
| void UnixAPIChecker::CheckPthreadOnce(CheckerContext &C, |
| const CallExpr *CE) const { |
| |
| // This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker. |
| // They can possibly be refactored. |
| |
| if (CE->getNumArgs() < 1) |
| return; |
| |
| // Check if the first argument is stack allocated. If so, issue a warning |
| // because that's likely to be bad news. |
| ProgramStateRef state = C.getState(); |
| const MemRegion *R = |
| state->getSVal(CE->getArg(0), C.getLocationContext()).getAsRegion(); |
| if (!R || !isa<StackSpaceRegion>(R->getMemorySpace())) |
| return; |
| |
| ExplodedNode *N = C.generateSink(state); |
| if (!N) |
| return; |
| |
| SmallString<256> S; |
| llvm::raw_svector_ostream os(S); |
| os << "Call to 'pthread_once' uses"; |
| if (const VarRegion *VR = dyn_cast<VarRegion>(R)) |
| os << " the local variable '" << VR->getDecl()->getName() << '\''; |
| else |
| os << " stack allocated memory"; |
| os << " for the \"control\" value. Using such transient memory for " |
| "the control value is potentially dangerous."; |
| if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace())) |
| os << " Perhaps you intended to declare the variable as 'static'?"; |
| |
| LazyInitialize(BT_pthreadOnce, "Improper use of 'pthread_once'"); |
| |
| BugReport *report = new BugReport(*BT_pthreadOnce, os.str(), N); |
| report->addRange(CE->getArg(0)->getSourceRange()); |
| C.EmitReport(report); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // "calloc", "malloc", "realloc", "alloca" and "valloc" with allocation size 0 |
| //===----------------------------------------------------------------------===// |
| // FIXME: Eventually these should be rolled into the MallocChecker, but right now |
| // they're more basic and valuable for widespread use. |
| |
| // Returns true if we try to do a zero byte allocation, false otherwise. |
| // Fills in trueState and falseState. |
| static bool IsZeroByteAllocation(ProgramStateRef state, |
| const SVal argVal, |
| ProgramStateRef *trueState, |
| ProgramStateRef *falseState) { |
| llvm::tie(*trueState, *falseState) = |
| state->assume(cast<DefinedSVal>(argVal)); |
| |
| return (*falseState && !*trueState); |
| } |
| |
| // Generates an error report, indicating that the function whose name is given |
| // will perform a zero byte allocation. |
| // Returns false if an error occured, true otherwise. |
| bool UnixAPIChecker::ReportZeroByteAllocation(CheckerContext &C, |
| ProgramStateRef falseState, |
| const Expr *arg, |
| const char *fn_name) const { |
| ExplodedNode *N = C.generateSink(falseState); |
| if (!N) |
| return false; |
| |
| LazyInitialize(BT_mallocZero, |
| "Undefined allocation of 0 bytes (CERT MEM04-C; CWE-131)"); |
| |
| SmallString<256> S; |
| llvm::raw_svector_ostream os(S); |
| os << "Call to '" << fn_name << "' has an allocation size of 0 bytes"; |
| BugReport *report = new BugReport(*BT_mallocZero, os.str(), N); |
| |
| report->addRange(arg->getSourceRange()); |
| report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, arg, |
| report)); |
| C.EmitReport(report); |
| |
| return true; |
| } |
| |
| // Does a basic check for 0-sized allocations suitable for most of the below |
| // functions (modulo "calloc") |
| void UnixAPIChecker::BasicAllocationCheck(CheckerContext &C, |
| const CallExpr *CE, |
| const unsigned numArgs, |
| const unsigned sizeArg, |
| const char *fn) const { |
| // Sanity check for the correct number of arguments |
| if (CE->getNumArgs() != numArgs) |
| return; |
| |
| // Check if the allocation size is 0. |
| ProgramStateRef state = C.getState(); |
| ProgramStateRef trueState = NULL, falseState = NULL; |
| const Expr *arg = CE->getArg(sizeArg); |
| SVal argVal = state->getSVal(arg, C.getLocationContext()); |
| |
| if (argVal.isUnknownOrUndef()) |
| return; |
| |
| // Is the value perfectly constrained to zero? |
| if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) { |
| (void) ReportZeroByteAllocation(C, falseState, arg, fn); |
| return; |
| } |
| // Assume the the value is non-zero going forward. |
| assert(trueState); |
| if (trueState != state) |
| C.addTransition(trueState); |
| } |
| |
| void UnixAPIChecker::CheckCallocZero(CheckerContext &C, |
| const CallExpr *CE) const { |
| unsigned int nArgs = CE->getNumArgs(); |
| if (nArgs != 2) |
| return; |
| |
| ProgramStateRef state = C.getState(); |
| ProgramStateRef trueState = NULL, falseState = NULL; |
| |
| unsigned int i; |
| for (i = 0; i < nArgs; i++) { |
| const Expr *arg = CE->getArg(i); |
| SVal argVal = state->getSVal(arg, C.getLocationContext()); |
| if (argVal.isUnknownOrUndef()) { |
| if (i == 0) |
| continue; |
| else |
| return; |
| } |
| |
| if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) { |
| if (ReportZeroByteAllocation(C, falseState, arg, "calloc")) |
| return; |
| else if (i == 0) |
| continue; |
| else |
| return; |
| } |
| } |
| |
| // Assume the the value is non-zero going forward. |
| assert(trueState); |
| if (trueState != state) |
| C.addTransition(trueState); |
| } |
| |
| void UnixAPIChecker::CheckMallocZero(CheckerContext &C, |
| const CallExpr *CE) const { |
| BasicAllocationCheck(C, CE, 1, 0, "malloc"); |
| } |
| |
| void UnixAPIChecker::CheckReallocZero(CheckerContext &C, |
| const CallExpr *CE) const { |
| BasicAllocationCheck(C, CE, 2, 1, "realloc"); |
| } |
| |
| void UnixAPIChecker::CheckAllocaZero(CheckerContext &C, |
| const CallExpr *CE) const { |
| BasicAllocationCheck(C, CE, 1, 0, "alloca"); |
| } |
| |
| void UnixAPIChecker::CheckVallocZero(CheckerContext &C, |
| const CallExpr *CE) const { |
| BasicAllocationCheck(C, CE, 1, 0, "valloc"); |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // Central dispatch function. |
| //===----------------------------------------------------------------------===// |
| |
| void UnixAPIChecker::checkPreStmt(const CallExpr *CE, |
| CheckerContext &C) const { |
| StringRef FName = C.getCalleeName(CE); |
| if (FName.empty()) |
| return; |
| |
| SubChecker SC = |
| llvm::StringSwitch<SubChecker>(FName) |
| .Case("open", &UnixAPIChecker::CheckOpen) |
| .Case("pthread_once", &UnixAPIChecker::CheckPthreadOnce) |
| .Case("calloc", &UnixAPIChecker::CheckCallocZero) |
| .Case("malloc", &UnixAPIChecker::CheckMallocZero) |
| .Case("realloc", &UnixAPIChecker::CheckReallocZero) |
| .Cases("alloca", "__builtin_alloca", &UnixAPIChecker::CheckAllocaZero) |
| .Case("valloc", &UnixAPIChecker::CheckVallocZero) |
| .Default(NULL); |
| |
| if (SC) |
| (this->*SC)(C, CE); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Registration. |
| //===----------------------------------------------------------------------===// |
| |
| void ento::registerUnixAPIChecker(CheckerManager &mgr) { |
| mgr.registerChecker<UnixAPIChecker>(); |
| } |