1 //= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- C++ -*-//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This defines UnixAPIChecker, which is an assortment of checks on calls
11 // to various, widely used UNIX/Posix functions.
13 //===----------------------------------------------------------------------===//
15 #include "ClangSACheckers.h"
16 #include "clang/StaticAnalyzer/Core/Checker.h"
17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
20 #include "clang/Basic/TargetInfo.h"
21 #include "llvm/ADT/Optional.h"
22 #include "llvm/ADT/SmallString.h"
23 #include "llvm/ADT/STLExtras.h"
24 #include "llvm/ADT/StringSwitch.h"
27 using namespace clang;
32 class UnixAPIChecker : public Checker< check::PreStmt<CallExpr> > {
33 mutable OwningPtr<BugType> BT_open, BT_pthreadOnce, BT_mallocZero;
34 mutable Optional<uint64_t> Val_O_CREAT;
37 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
39 void CheckOpen(CheckerContext &C, const CallExpr *CE) const;
40 void CheckPthreadOnce(CheckerContext &C, const CallExpr *CE) const;
41 void CheckCallocZero(CheckerContext &C, const CallExpr *CE) const;
42 void CheckMallocZero(CheckerContext &C, const CallExpr *CE) const;
43 void CheckReallocZero(CheckerContext &C, const CallExpr *CE) const;
44 void CheckReallocfZero(CheckerContext &C, const CallExpr *CE) const;
45 void CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const;
46 void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const;
48 typedef void (UnixAPIChecker::*SubChecker)(CheckerContext &,
49 const CallExpr *) const;
51 bool ReportZeroByteAllocation(CheckerContext &C,
52 ProgramStateRef falseState,
54 const char *fn_name) const;
55 void BasicAllocationCheck(CheckerContext &C,
57 const unsigned numArgs,
58 const unsigned sizeArg,
59 const char *fn) const;
61 } //end anonymous namespace
63 //===----------------------------------------------------------------------===//
65 //===----------------------------------------------------------------------===//
67 static inline void LazyInitialize(OwningPtr<BugType> &BT,
71 BT.reset(new BugType(name, categories::UnixAPI));
74 //===----------------------------------------------------------------------===//
75 // "open" (man 2 open)
76 //===----------------------------------------------------------------------===//
78 void UnixAPIChecker::CheckOpen(CheckerContext &C, const CallExpr *CE) const {
79 // The definition of O_CREAT is platform specific. We need a better way
80 // of querying this information from the checking environment.
81 if (!Val_O_CREAT.hasValue()) {
82 if (C.getASTContext().getTargetInfo().getTriple().getVendor()
83 == llvm::Triple::Apple)
86 // FIXME: We need a more general way of getting the O_CREAT value.
87 // We could possibly grovel through the preprocessor state, but
88 // that would require passing the Preprocessor object to the ExprEngine.
93 // Look at the 'oflags' argument for the O_CREAT flag.
94 ProgramStateRef state = C.getState();
96 if (CE->getNumArgs() < 2) {
97 // The frontend should issue a warning for this case, so this is a sanity
102 // Now check if oflags has O_CREAT set.
103 const Expr *oflagsEx = CE->getArg(1);
104 const SVal V = state->getSVal(oflagsEx, C.getLocationContext());
105 if (!isa<NonLoc>(V)) {
106 // The case where 'V' can be a location can only be due to a bad header,
107 // so in this case bail out.
110 NonLoc oflags = cast<NonLoc>(V);
112 cast<NonLoc>(C.getSValBuilder().makeIntVal(Val_O_CREAT.getValue(),
113 oflagsEx->getType()));
114 SVal maskedFlagsUC = C.getSValBuilder().evalBinOpNN(state, BO_And,
116 oflagsEx->getType());
117 if (maskedFlagsUC.isUnknownOrUndef())
119 DefinedSVal maskedFlags = cast<DefinedSVal>(maskedFlagsUC);
121 // Check if maskedFlags is non-zero.
122 ProgramStateRef trueState, falseState;
123 llvm::tie(trueState, falseState) = state->assume(maskedFlags);
125 // Only emit an error if the value of 'maskedFlags' is properly
127 if (!(trueState && !falseState))
130 if (CE->getNumArgs() < 3) {
131 ExplodedNode *N = C.generateSink(trueState);
135 LazyInitialize(BT_open, "Improper use of 'open'");
138 new BugReport(*BT_open,
139 "Call to 'open' requires a third argument when "
140 "the 'O_CREAT' flag is set", N);
141 report->addRange(oflagsEx->getSourceRange());
142 C.emitReport(report);
146 //===----------------------------------------------------------------------===//
148 //===----------------------------------------------------------------------===//
150 void UnixAPIChecker::CheckPthreadOnce(CheckerContext &C,
151 const CallExpr *CE) const {
153 // This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker.
154 // They can possibly be refactored.
156 if (CE->getNumArgs() < 1)
159 // Check if the first argument is stack allocated. If so, issue a warning
160 // because that's likely to be bad news.
161 ProgramStateRef state = C.getState();
163 state->getSVal(CE->getArg(0), C.getLocationContext()).getAsRegion();
164 if (!R || !isa<StackSpaceRegion>(R->getMemorySpace()))
167 ExplodedNode *N = C.generateSink(state);
172 llvm::raw_svector_ostream os(S);
173 os << "Call to 'pthread_once' uses";
174 if (const VarRegion *VR = dyn_cast<VarRegion>(R))
175 os << " the local variable '" << VR->getDecl()->getName() << '\'';
177 os << " stack allocated memory";
178 os << " for the \"control\" value. Using such transient memory for "
179 "the control value is potentially dangerous.";
180 if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace()))
181 os << " Perhaps you intended to declare the variable as 'static'?";
183 LazyInitialize(BT_pthreadOnce, "Improper use of 'pthread_once'");
185 BugReport *report = new BugReport(*BT_pthreadOnce, os.str(), N);
186 report->addRange(CE->getArg(0)->getSourceRange());
187 C.emitReport(report);
190 //===----------------------------------------------------------------------===//
191 // "calloc", "malloc", "realloc", "reallocf", "alloca" and "valloc"
192 // with allocation size 0
193 //===----------------------------------------------------------------------===//
194 // FIXME: Eventually these should be rolled into the MallocChecker, but right now
195 // they're more basic and valuable for widespread use.
197 // Returns true if we try to do a zero byte allocation, false otherwise.
198 // Fills in trueState and falseState.
199 static bool IsZeroByteAllocation(ProgramStateRef state,
201 ProgramStateRef *trueState,
202 ProgramStateRef *falseState) {
203 llvm::tie(*trueState, *falseState) =
204 state->assume(cast<DefinedSVal>(argVal));
206 return (*falseState && !*trueState);
209 // Generates an error report, indicating that the function whose name is given
210 // will perform a zero byte allocation.
211 // Returns false if an error occured, true otherwise.
212 bool UnixAPIChecker::ReportZeroByteAllocation(CheckerContext &C,
213 ProgramStateRef falseState,
215 const char *fn_name) const {
216 ExplodedNode *N = C.generateSink(falseState);
220 LazyInitialize(BT_mallocZero,
221 "Undefined allocation of 0 bytes (CERT MEM04-C; CWE-131)");
224 llvm::raw_svector_ostream os(S);
225 os << "Call to '" << fn_name << "' has an allocation size of 0 bytes";
226 BugReport *report = new BugReport(*BT_mallocZero, os.str(), N);
228 report->addRange(arg->getSourceRange());
229 bugreporter::trackNullOrUndefValue(N, arg, *report);
230 C.emitReport(report);
235 // Does a basic check for 0-sized allocations suitable for most of the below
236 // functions (modulo "calloc")
237 void UnixAPIChecker::BasicAllocationCheck(CheckerContext &C,
239 const unsigned numArgs,
240 const unsigned sizeArg,
241 const char *fn) const {
242 // Sanity check for the correct number of arguments
243 if (CE->getNumArgs() != numArgs)
246 // Check if the allocation size is 0.
247 ProgramStateRef state = C.getState();
248 ProgramStateRef trueState = NULL, falseState = NULL;
249 const Expr *arg = CE->getArg(sizeArg);
250 SVal argVal = state->getSVal(arg, C.getLocationContext());
252 if (argVal.isUnknownOrUndef())
255 // Is the value perfectly constrained to zero?
256 if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
257 (void) ReportZeroByteAllocation(C, falseState, arg, fn);
260 // Assume the value is non-zero going forward.
262 if (trueState != state)
263 C.addTransition(trueState);
266 void UnixAPIChecker::CheckCallocZero(CheckerContext &C,
267 const CallExpr *CE) const {
268 unsigned int nArgs = CE->getNumArgs();
272 ProgramStateRef state = C.getState();
273 ProgramStateRef trueState = NULL, falseState = NULL;
276 for (i = 0; i < nArgs; i++) {
277 const Expr *arg = CE->getArg(i);
278 SVal argVal = state->getSVal(arg, C.getLocationContext());
279 if (argVal.isUnknownOrUndef()) {
286 if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
287 if (ReportZeroByteAllocation(C, falseState, arg, "calloc"))
296 // Assume the value is non-zero going forward.
298 if (trueState != state)
299 C.addTransition(trueState);
302 void UnixAPIChecker::CheckMallocZero(CheckerContext &C,
303 const CallExpr *CE) const {
304 BasicAllocationCheck(C, CE, 1, 0, "malloc");
307 void UnixAPIChecker::CheckReallocZero(CheckerContext &C,
308 const CallExpr *CE) const {
309 BasicAllocationCheck(C, CE, 2, 1, "realloc");
312 void UnixAPIChecker::CheckReallocfZero(CheckerContext &C,
313 const CallExpr *CE) const {
314 BasicAllocationCheck(C, CE, 2, 1, "reallocf");
317 void UnixAPIChecker::CheckAllocaZero(CheckerContext &C,
318 const CallExpr *CE) const {
319 BasicAllocationCheck(C, CE, 1, 0, "alloca");
322 void UnixAPIChecker::CheckVallocZero(CheckerContext &C,
323 const CallExpr *CE) const {
324 BasicAllocationCheck(C, CE, 1, 0, "valloc");
328 //===----------------------------------------------------------------------===//
329 // Central dispatch function.
330 //===----------------------------------------------------------------------===//
332 void UnixAPIChecker::checkPreStmt(const CallExpr *CE,
333 CheckerContext &C) const {
334 const FunctionDecl *FD = C.getCalleeDecl(CE);
335 if (!FD || FD->getKind() != Decl::Function)
338 StringRef FName = C.getCalleeName(FD);
343 llvm::StringSwitch<SubChecker>(FName)
344 .Case("open", &UnixAPIChecker::CheckOpen)
345 .Case("pthread_once", &UnixAPIChecker::CheckPthreadOnce)
346 .Case("calloc", &UnixAPIChecker::CheckCallocZero)
347 .Case("malloc", &UnixAPIChecker::CheckMallocZero)
348 .Case("realloc", &UnixAPIChecker::CheckReallocZero)
349 .Case("reallocf", &UnixAPIChecker::CheckReallocfZero)
350 .Cases("alloca", "__builtin_alloca", &UnixAPIChecker::CheckAllocaZero)
351 .Case("valloc", &UnixAPIChecker::CheckVallocZero)
358 //===----------------------------------------------------------------------===//
360 //===----------------------------------------------------------------------===//
362 void ento::registerUnixAPIChecker(CheckerManager &mgr) {
363 mgr.registerChecker<UnixAPIChecker>();