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 CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const;
45 void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const;
47 typedef void (UnixAPIChecker::*SubChecker)(CheckerContext &,
48 const CallExpr *) const;
50 bool ReportZeroByteAllocation(CheckerContext &C,
51 ProgramStateRef falseState,
53 const char *fn_name) const;
54 void BasicAllocationCheck(CheckerContext &C,
56 const unsigned numArgs,
57 const unsigned sizeArg,
58 const char *fn) const;
60 } //end anonymous namespace
62 //===----------------------------------------------------------------------===//
64 //===----------------------------------------------------------------------===//
66 static inline void LazyInitialize(OwningPtr<BugType> &BT,
70 BT.reset(new BugType(name, categories::UnixAPI));
73 //===----------------------------------------------------------------------===//
74 // "open" (man 2 open)
75 //===----------------------------------------------------------------------===//
77 void UnixAPIChecker::CheckOpen(CheckerContext &C, const CallExpr *CE) const {
78 // The definition of O_CREAT is platform specific. We need a better way
79 // of querying this information from the checking environment.
80 if (!Val_O_CREAT.hasValue()) {
81 if (C.getASTContext().getTargetInfo().getTriple().getVendor()
82 == llvm::Triple::Apple)
85 // FIXME: We need a more general way of getting the O_CREAT value.
86 // We could possibly grovel through the preprocessor state, but
87 // that would require passing the Preprocessor object to the ExprEngine.
92 // Look at the 'oflags' argument for the O_CREAT flag.
93 ProgramStateRef state = C.getState();
95 if (CE->getNumArgs() < 2) {
96 // The frontend should issue a warning for this case, so this is a sanity
101 // Now check if oflags has O_CREAT set.
102 const Expr *oflagsEx = CE->getArg(1);
103 const SVal V = state->getSVal(oflagsEx, C.getLocationContext());
104 if (!isa<NonLoc>(V)) {
105 // The case where 'V' can be a location can only be due to a bad header,
106 // so in this case bail out.
109 NonLoc oflags = cast<NonLoc>(V);
111 cast<NonLoc>(C.getSValBuilder().makeIntVal(Val_O_CREAT.getValue(),
112 oflagsEx->getType()));
113 SVal maskedFlagsUC = C.getSValBuilder().evalBinOpNN(state, BO_And,
115 oflagsEx->getType());
116 if (maskedFlagsUC.isUnknownOrUndef())
118 DefinedSVal maskedFlags = cast<DefinedSVal>(maskedFlagsUC);
120 // Check if maskedFlags is non-zero.
121 ProgramStateRef trueState, falseState;
122 llvm::tie(trueState, falseState) = state->assume(maskedFlags);
124 // Only emit an error if the value of 'maskedFlags' is properly
126 if (!(trueState && !falseState))
129 if (CE->getNumArgs() < 3) {
130 ExplodedNode *N = C.generateSink(trueState);
134 LazyInitialize(BT_open, "Improper use of 'open'");
137 new BugReport(*BT_open,
138 "Call to 'open' requires a third argument when "
139 "the 'O_CREAT' flag is set", N);
140 report->addRange(oflagsEx->getSourceRange());
141 C.EmitReport(report);
145 //===----------------------------------------------------------------------===//
147 //===----------------------------------------------------------------------===//
149 void UnixAPIChecker::CheckPthreadOnce(CheckerContext &C,
150 const CallExpr *CE) const {
152 // This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker.
153 // They can possibly be refactored.
155 if (CE->getNumArgs() < 1)
158 // Check if the first argument is stack allocated. If so, issue a warning
159 // because that's likely to be bad news.
160 ProgramStateRef state = C.getState();
162 state->getSVal(CE->getArg(0), C.getLocationContext()).getAsRegion();
163 if (!R || !isa<StackSpaceRegion>(R->getMemorySpace()))
166 ExplodedNode *N = C.generateSink(state);
171 llvm::raw_svector_ostream os(S);
172 os << "Call to 'pthread_once' uses";
173 if (const VarRegion *VR = dyn_cast<VarRegion>(R))
174 os << " the local variable '" << VR->getDecl()->getName() << '\'';
176 os << " stack allocated memory";
177 os << " for the \"control\" value. Using such transient memory for "
178 "the control value is potentially dangerous.";
179 if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace()))
180 os << " Perhaps you intended to declare the variable as 'static'?";
182 LazyInitialize(BT_pthreadOnce, "Improper use of 'pthread_once'");
184 BugReport *report = new BugReport(*BT_pthreadOnce, os.str(), N);
185 report->addRange(CE->getArg(0)->getSourceRange());
186 C.EmitReport(report);
189 //===----------------------------------------------------------------------===//
190 // "calloc", "malloc", "realloc", "alloca" and "valloc" with allocation size 0
191 //===----------------------------------------------------------------------===//
192 // FIXME: Eventually these should be rolled into the MallocChecker, but right now
193 // they're more basic and valuable for widespread use.
195 // Returns true if we try to do a zero byte allocation, false otherwise.
196 // Fills in trueState and falseState.
197 static bool IsZeroByteAllocation(ProgramStateRef state,
199 ProgramStateRef *trueState,
200 ProgramStateRef *falseState) {
201 llvm::tie(*trueState, *falseState) =
202 state->assume(cast<DefinedSVal>(argVal));
204 return (*falseState && !*trueState);
207 // Generates an error report, indicating that the function whose name is given
208 // will perform a zero byte allocation.
209 // Returns false if an error occured, true otherwise.
210 bool UnixAPIChecker::ReportZeroByteAllocation(CheckerContext &C,
211 ProgramStateRef falseState,
213 const char *fn_name) const {
214 ExplodedNode *N = C.generateSink(falseState);
218 LazyInitialize(BT_mallocZero,
219 "Undefined allocation of 0 bytes (CERT MEM04-C; CWE-131)");
222 llvm::raw_svector_ostream os(S);
223 os << "Call to '" << fn_name << "' has an allocation size of 0 bytes";
224 BugReport *report = new BugReport(*BT_mallocZero, os.str(), N);
226 report->addRange(arg->getSourceRange());
227 report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, arg,
229 C.EmitReport(report);
234 // Does a basic check for 0-sized allocations suitable for most of the below
235 // functions (modulo "calloc")
236 void UnixAPIChecker::BasicAllocationCheck(CheckerContext &C,
238 const unsigned numArgs,
239 const unsigned sizeArg,
240 const char *fn) const {
241 // Sanity check for the correct number of arguments
242 if (CE->getNumArgs() != numArgs)
245 // Check if the allocation size is 0.
246 ProgramStateRef state = C.getState();
247 ProgramStateRef trueState = NULL, falseState = NULL;
248 const Expr *arg = CE->getArg(sizeArg);
249 SVal argVal = state->getSVal(arg, C.getLocationContext());
251 if (argVal.isUnknownOrUndef())
254 // Is the value perfectly constrained to zero?
255 if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
256 (void) ReportZeroByteAllocation(C, falseState, arg, fn);
259 // Assume the the value is non-zero going forward.
261 if (trueState != state)
262 C.addTransition(trueState);
265 void UnixAPIChecker::CheckCallocZero(CheckerContext &C,
266 const CallExpr *CE) const {
267 unsigned int nArgs = CE->getNumArgs();
271 ProgramStateRef state = C.getState();
272 ProgramStateRef trueState = NULL, falseState = NULL;
275 for (i = 0; i < nArgs; i++) {
276 const Expr *arg = CE->getArg(i);
277 SVal argVal = state->getSVal(arg, C.getLocationContext());
278 if (argVal.isUnknownOrUndef()) {
285 if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
286 if (ReportZeroByteAllocation(C, falseState, arg, "calloc"))
295 // Assume the the value is non-zero going forward.
297 if (trueState != state)
298 C.addTransition(trueState);
301 void UnixAPIChecker::CheckMallocZero(CheckerContext &C,
302 const CallExpr *CE) const {
303 BasicAllocationCheck(C, CE, 1, 0, "malloc");
306 void UnixAPIChecker::CheckReallocZero(CheckerContext &C,
307 const CallExpr *CE) const {
308 BasicAllocationCheck(C, CE, 2, 1, "realloc");
311 void UnixAPIChecker::CheckAllocaZero(CheckerContext &C,
312 const CallExpr *CE) const {
313 BasicAllocationCheck(C, CE, 1, 0, "alloca");
316 void UnixAPIChecker::CheckVallocZero(CheckerContext &C,
317 const CallExpr *CE) const {
318 BasicAllocationCheck(C, CE, 1, 0, "valloc");
322 //===----------------------------------------------------------------------===//
323 // Central dispatch function.
324 //===----------------------------------------------------------------------===//
326 void UnixAPIChecker::checkPreStmt(const CallExpr *CE,
327 CheckerContext &C) const {
328 StringRef FName = C.getCalleeName(CE);
333 llvm::StringSwitch<SubChecker>(FName)
334 .Case("open", &UnixAPIChecker::CheckOpen)
335 .Case("pthread_once", &UnixAPIChecker::CheckPthreadOnce)
336 .Case("calloc", &UnixAPIChecker::CheckCallocZero)
337 .Case("malloc", &UnixAPIChecker::CheckMallocZero)
338 .Case("realloc", &UnixAPIChecker::CheckReallocZero)
339 .Cases("alloca", "__builtin_alloca", &UnixAPIChecker::CheckAllocaZero)
340 .Case("valloc", &UnixAPIChecker::CheckVallocZero)
347 //===----------------------------------------------------------------------===//
349 //===----------------------------------------------------------------------===//
351 void ento::registerUnixAPIChecker(CheckerManager &mgr) {
352 mgr.registerChecker<UnixAPIChecker>();