| //= 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/StringSwitch.h" |
| #include <fcntl.h> |
| |
| using namespace clang; |
| using namespace ento; |
| using llvm::Optional; |
| |
| namespace { |
| class UnixAPIChecker : public Checker< check::PreStmt<CallExpr> > { |
| mutable llvm::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 CheckMallocZero(CheckerContext &C, const CallExpr *CE) const; |
| |
| typedef void (UnixAPIChecker::*SubChecker)(CheckerContext &, |
| const CallExpr *) const; |
| }; |
| } //end anonymous namespace |
| |
| //===----------------------------------------------------------------------===// |
| // Utility functions. |
| //===----------------------------------------------------------------------===// |
| |
| static inline void LazyInitialize(llvm::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().Target.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. |
| const ProgramState *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); |
| 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. |
| const ProgramState *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'"); |
| |
| RangedBugReport *report = |
| new RangedBugReport(*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. |
| const ProgramState *state = C.getState(); |
| const MemRegion *R = state->getSVal(CE->getArg(0)).getAsRegion(); |
| if (!R || !isa<StackSpaceRegion>(R->getMemorySpace())) |
| return; |
| |
| ExplodedNode *N = C.generateSink(state); |
| if (!N) |
| return; |
| |
| llvm::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'"); |
| |
| RangedBugReport *report = new RangedBugReport(*BT_pthreadOnce, os.str(), N); |
| report->addRange(CE->getArg(0)->getSourceRange()); |
| C.EmitReport(report); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // "malloc" with allocation size 0 |
| //===----------------------------------------------------------------------===// |
| |
| // FIXME: Eventually this should be rolled into the MallocChecker, but this |
| // check is more basic and is valuable for widespread use. |
| void UnixAPIChecker::CheckMallocZero(CheckerContext &C, |
| const CallExpr *CE) const { |
| |
| // Sanity check that malloc takes one argument. |
| if (CE->getNumArgs() != 1) |
| return; |
| |
| // Check if the allocation size is 0. |
| const ProgramState *state = C.getState(); |
| SVal argVal = state->getSVal(CE->getArg(0)); |
| |
| if (argVal.isUnknownOrUndef()) |
| return; |
| |
| const ProgramState *trueState, *falseState; |
| llvm::tie(trueState, falseState) = state->assume(cast<DefinedSVal>(argVal)); |
| |
| // Is the value perfectly constrained to zero? |
| if (falseState && !trueState) { |
| ExplodedNode *N = C.generateSink(falseState); |
| if (!N) |
| return; |
| |
| // FIXME: Add reference to CERT advisory, and/or C99 standard in bug |
| // output. |
| |
| LazyInitialize(BT_mallocZero, "Undefined allocation of 0 bytes"); |
| |
| EnhancedBugReport *report = |
| new EnhancedBugReport(*BT_mallocZero, "Call to 'malloc' has an allocation" |
| " size of 0 bytes", N); |
| report->addRange(CE->getArg(0)->getSourceRange()); |
| report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, |
| CE->getArg(0)); |
| C.EmitReport(report); |
| return; |
| } |
| // Assume the the value is non-zero going forward. |
| assert(trueState); |
| if (trueState != state) { |
| C.addTransition(trueState); |
| } |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Central dispatch function. |
| //===----------------------------------------------------------------------===// |
| |
| void UnixAPIChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const { |
| // Get the callee. All the functions we care about are C functions |
| // with simple identifiers. |
| const ProgramState *state = C.getState(); |
| const Expr *Callee = CE->getCallee(); |
| const FunctionDecl *Fn = state->getSVal(Callee).getAsFunctionDecl(); |
| |
| if (!Fn) |
| return; |
| |
| const IdentifierInfo *FI = Fn->getIdentifier(); |
| if (!FI) |
| return; |
| |
| SubChecker SC = |
| llvm::StringSwitch<SubChecker>(FI->getName()) |
| .Case("open", &UnixAPIChecker::CheckOpen) |
| .Case("pthread_once", &UnixAPIChecker::CheckPthreadOnce) |
| .Case("malloc", &UnixAPIChecker::CheckMallocZero) |
| .Default(NULL); |
| |
| if (SC) |
| (this->*SC)(C, CE); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Registration. |
| //===----------------------------------------------------------------------===// |
| |
| void ento::registerUnixAPIChecker(CheckerManager &mgr) { |
| mgr.registerChecker<UnixAPIChecker>(); |
| } |