CStringChecker.cpp revision 685379965c1b105ce89cf4f6c60810932b7f4d0d
15821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//= CStringChecker.cpp - Checks calls to C string functions --------*- C++ -*-// 25821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 35821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// The LLVM Compiler Infrastructure 45821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 55821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This file is distributed under the University of Illinois Open Source 65821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// License. See LICENSE.TXT for details. 7eb525c5499e34cc9c4b825d6d9e75bb07cc06aceBen Murdoch// 85821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===----------------------------------------------------------------------===// 95821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This defines CStringChecker, which is an assortment of checks on calls 115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// to functions in <string.h>. 125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===----------------------------------------------------------------------===// 145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "ClangSACheckers.h" 161320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci#include "InterCheckerAPI.h" 171320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci#include "clang/StaticAnalyzer/Core/Checker.h" 185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/StaticAnalyzer/Core/CheckerManager.h" 195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h" 221320f92c476a1ad9d19dba2a48c72b75566198e9Primiano Tucci#include "llvm/ADT/SmallString.h" 235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/ADT/STLExtras.h" 245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/ADT/StringSwitch.h" 255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)using namespace clang; 275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)using namespace ento; 285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)namespace { 305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)class CStringChecker : public Checker< eval::Call, 315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) check::PreStmt<DeclStmt>, 325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) check::LiveSymbols, 335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) check::DeadSymbols, 345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) check::RegionChanges 355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) > { 365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) mutable OwningPtr<BugType> BT_Null, 375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BT_Bounds, 385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BT_Overlap, 395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BT_NotCString, 405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BT_AdditionOverflow; 415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) mutable const char *CurrentFunctionDescription; 435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)public: 455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) /// The filter is used to filter out the diagnostics which are not enabled by 465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) /// the user. 475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) struct CStringChecksFilter { 485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DefaultBool CheckCStringNullArg; 495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DefaultBool CheckCStringOutOfBounds; 505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DefaultBool CheckCStringBufferOverlap; 515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DefaultBool CheckCStringNotNullTerm; 525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) }; 535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) CStringChecksFilter Filter; 555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) static void *getTag() { static int tag; return &tag; } 575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool evalCall(const CallExpr *CE, CheckerContext &C) const; 595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void checkPreStmt(const DeclStmt *DS, CheckerContext &C) const; 605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void checkLiveSymbols(ProgramStateRef state, SymbolReaper &SR) const; 61 void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const; 62 bool wantsRegionChangeUpdate(ProgramStateRef state) const; 63 64 ProgramStateRef 65 checkRegionChanges(ProgramStateRef state, 66 const StoreManager::InvalidatedSymbols *, 67 ArrayRef<const MemRegion *> ExplicitRegions, 68 ArrayRef<const MemRegion *> Regions, 69 const CallEvent *Call) const; 70 71 typedef void (CStringChecker::*FnCheck)(CheckerContext &, 72 const CallExpr *) const; 73 74 void evalMemcpy(CheckerContext &C, const CallExpr *CE) const; 75 void evalMempcpy(CheckerContext &C, const CallExpr *CE) const; 76 void evalMemmove(CheckerContext &C, const CallExpr *CE) const; 77 void evalBcopy(CheckerContext &C, const CallExpr *CE) const; 78 void evalCopyCommon(CheckerContext &C, const CallExpr *CE, 79 ProgramStateRef state, 80 const Expr *Size, 81 const Expr *Source, 82 const Expr *Dest, 83 bool Restricted = false, 84 bool IsMempcpy = false) const; 85 86 void evalMemcmp(CheckerContext &C, const CallExpr *CE) const; 87 88 void evalstrLength(CheckerContext &C, const CallExpr *CE) const; 89 void evalstrnLength(CheckerContext &C, const CallExpr *CE) const; 90 void evalstrLengthCommon(CheckerContext &C, 91 const CallExpr *CE, 92 bool IsStrnlen = false) const; 93 94 void evalStrcpy(CheckerContext &C, const CallExpr *CE) const; 95 void evalStrncpy(CheckerContext &C, const CallExpr *CE) const; 96 void evalStpcpy(CheckerContext &C, const CallExpr *CE) const; 97 void evalStrcpyCommon(CheckerContext &C, 98 const CallExpr *CE, 99 bool returnEnd, 100 bool isBounded, 101 bool isAppending) const; 102 103 void evalStrcat(CheckerContext &C, const CallExpr *CE) const; 104 void evalStrncat(CheckerContext &C, const CallExpr *CE) const; 105 106 void evalStrcmp(CheckerContext &C, const CallExpr *CE) const; 107 void evalStrncmp(CheckerContext &C, const CallExpr *CE) const; 108 void evalStrcasecmp(CheckerContext &C, const CallExpr *CE) const; 109 void evalStrncasecmp(CheckerContext &C, const CallExpr *CE) const; 110 void evalStrcmpCommon(CheckerContext &C, 111 const CallExpr *CE, 112 bool isBounded = false, 113 bool ignoreCase = false) const; 114 115 // Utility methods 116 std::pair<ProgramStateRef , ProgramStateRef > 117 static assumeZero(CheckerContext &C, 118 ProgramStateRef state, SVal V, QualType Ty); 119 120 static ProgramStateRef setCStringLength(ProgramStateRef state, 121 const MemRegion *MR, 122 SVal strLength); 123 static SVal getCStringLengthForRegion(CheckerContext &C, 124 ProgramStateRef &state, 125 const Expr *Ex, 126 const MemRegion *MR, 127 bool hypothetical); 128 SVal getCStringLength(CheckerContext &C, 129 ProgramStateRef &state, 130 const Expr *Ex, 131 SVal Buf, 132 bool hypothetical = false) const; 133 134 const StringLiteral *getCStringLiteral(CheckerContext &C, 135 ProgramStateRef &state, 136 const Expr *expr, 137 SVal val) const; 138 139 static ProgramStateRef InvalidateBuffer(CheckerContext &C, 140 ProgramStateRef state, 141 const Expr *Ex, SVal V); 142 143 static bool SummarizeRegion(raw_ostream &os, ASTContext &Ctx, 144 const MemRegion *MR); 145 146 // Re-usable checks 147 ProgramStateRef checkNonNull(CheckerContext &C, 148 ProgramStateRef state, 149 const Expr *S, 150 SVal l) const; 151 ProgramStateRef CheckLocation(CheckerContext &C, 152 ProgramStateRef state, 153 const Expr *S, 154 SVal l, 155 const char *message = NULL) const; 156 ProgramStateRef CheckBufferAccess(CheckerContext &C, 157 ProgramStateRef state, 158 const Expr *Size, 159 const Expr *FirstBuf, 160 const Expr *SecondBuf, 161 const char *firstMessage = NULL, 162 const char *secondMessage = NULL, 163 bool WarnAboutSize = false) const; 164 165 ProgramStateRef CheckBufferAccess(CheckerContext &C, 166 ProgramStateRef state, 167 const Expr *Size, 168 const Expr *Buf, 169 const char *message = NULL, 170 bool WarnAboutSize = false) const { 171 // This is a convenience override. 172 return CheckBufferAccess(C, state, Size, Buf, NULL, message, NULL, 173 WarnAboutSize); 174 } 175 ProgramStateRef CheckOverlap(CheckerContext &C, 176 ProgramStateRef state, 177 const Expr *Size, 178 const Expr *First, 179 const Expr *Second) const; 180 void emitOverlapBug(CheckerContext &C, 181 ProgramStateRef state, 182 const Stmt *First, 183 const Stmt *Second) const; 184 185 ProgramStateRef checkAdditionOverflow(CheckerContext &C, 186 ProgramStateRef state, 187 NonLoc left, 188 NonLoc right) const; 189}; 190 191class CStringLength { 192public: 193 typedef llvm::ImmutableMap<const MemRegion *, SVal> EntryMap; 194}; 195} //end anonymous namespace 196 197namespace clang { 198namespace ento { 199 template <> 200 struct ProgramStateTrait<CStringLength> 201 : public ProgramStatePartialTrait<CStringLength::EntryMap> { 202 static void *GDMIndex() { return CStringChecker::getTag(); } 203 }; 204} 205} 206 207//===----------------------------------------------------------------------===// 208// Individual checks and utility methods. 209//===----------------------------------------------------------------------===// 210 211std::pair<ProgramStateRef , ProgramStateRef > 212CStringChecker::assumeZero(CheckerContext &C, ProgramStateRef state, SVal V, 213 QualType Ty) { 214 DefinedSVal *val = dyn_cast<DefinedSVal>(&V); 215 if (!val) 216 return std::pair<ProgramStateRef , ProgramStateRef >(state, state); 217 218 SValBuilder &svalBuilder = C.getSValBuilder(); 219 DefinedOrUnknownSVal zero = svalBuilder.makeZeroVal(Ty); 220 return state->assume(svalBuilder.evalEQ(state, *val, zero)); 221} 222 223ProgramStateRef CStringChecker::checkNonNull(CheckerContext &C, 224 ProgramStateRef state, 225 const Expr *S, SVal l) const { 226 // If a previous check has failed, propagate the failure. 227 if (!state) 228 return NULL; 229 230 ProgramStateRef stateNull, stateNonNull; 231 llvm::tie(stateNull, stateNonNull) = assumeZero(C, state, l, S->getType()); 232 233 if (stateNull && !stateNonNull) { 234 if (!Filter.CheckCStringNullArg) 235 return NULL; 236 237 ExplodedNode *N = C.generateSink(stateNull); 238 if (!N) 239 return NULL; 240 241 if (!BT_Null) 242 BT_Null.reset(new BuiltinBug("Unix API", 243 "Null pointer argument in call to byte string function")); 244 245 SmallString<80> buf; 246 llvm::raw_svector_ostream os(buf); 247 assert(CurrentFunctionDescription); 248 os << "Null pointer argument in call to " << CurrentFunctionDescription; 249 250 // Generate a report for this bug. 251 BuiltinBug *BT = static_cast<BuiltinBug*>(BT_Null.get()); 252 BugReport *report = new BugReport(*BT, os.str(), N); 253 254 report->addRange(S->getSourceRange()); 255 bugreporter::addTrackNullOrUndefValueVisitor(N, S, report); 256 C.EmitReport(report); 257 return NULL; 258 } 259 260 // From here on, assume that the value is non-null. 261 assert(stateNonNull); 262 return stateNonNull; 263} 264 265// FIXME: This was originally copied from ArrayBoundChecker.cpp. Refactor? 266ProgramStateRef CStringChecker::CheckLocation(CheckerContext &C, 267 ProgramStateRef state, 268 const Expr *S, SVal l, 269 const char *warningMsg) const { 270 // If a previous check has failed, propagate the failure. 271 if (!state) 272 return NULL; 273 274 // Check for out of bound array element access. 275 const MemRegion *R = l.getAsRegion(); 276 if (!R) 277 return state; 278 279 const ElementRegion *ER = dyn_cast<ElementRegion>(R); 280 if (!ER) 281 return state; 282 283 assert(ER->getValueType() == C.getASTContext().CharTy && 284 "CheckLocation should only be called with char* ElementRegions"); 285 286 // Get the size of the array. 287 const SubRegion *superReg = cast<SubRegion>(ER->getSuperRegion()); 288 SValBuilder &svalBuilder = C.getSValBuilder(); 289 SVal Extent = 290 svalBuilder.convertToArrayIndex(superReg->getExtent(svalBuilder)); 291 DefinedOrUnknownSVal Size = cast<DefinedOrUnknownSVal>(Extent); 292 293 // Get the index of the accessed element. 294 DefinedOrUnknownSVal Idx = cast<DefinedOrUnknownSVal>(ER->getIndex()); 295 296 ProgramStateRef StInBound = state->assumeInBound(Idx, Size, true); 297 ProgramStateRef StOutBound = state->assumeInBound(Idx, Size, false); 298 if (StOutBound && !StInBound) { 299 ExplodedNode *N = C.generateSink(StOutBound); 300 if (!N) 301 return NULL; 302 303 if (!BT_Bounds) { 304 BT_Bounds.reset(new BuiltinBug("Out-of-bound array access", 305 "Byte string function accesses out-of-bound array element")); 306 } 307 BuiltinBug *BT = static_cast<BuiltinBug*>(BT_Bounds.get()); 308 309 // Generate a report for this bug. 310 BugReport *report; 311 if (warningMsg) { 312 report = new BugReport(*BT, warningMsg, N); 313 } else { 314 assert(CurrentFunctionDescription); 315 assert(CurrentFunctionDescription[0] != '\0'); 316 317 SmallString<80> buf; 318 llvm::raw_svector_ostream os(buf); 319 os << (char)toupper(CurrentFunctionDescription[0]) 320 << &CurrentFunctionDescription[1] 321 << " accesses out-of-bound array element"; 322 report = new BugReport(*BT, os.str(), N); 323 } 324 325 // FIXME: It would be nice to eventually make this diagnostic more clear, 326 // e.g., by referencing the original declaration or by saying *why* this 327 // reference is outside the range. 328 329 report->addRange(S->getSourceRange()); 330 C.EmitReport(report); 331 return NULL; 332 } 333 334 // Array bound check succeeded. From this point forward the array bound 335 // should always succeed. 336 return StInBound; 337} 338 339ProgramStateRef CStringChecker::CheckBufferAccess(CheckerContext &C, 340 ProgramStateRef state, 341 const Expr *Size, 342 const Expr *FirstBuf, 343 const Expr *SecondBuf, 344 const char *firstMessage, 345 const char *secondMessage, 346 bool WarnAboutSize) const { 347 // If a previous check has failed, propagate the failure. 348 if (!state) 349 return NULL; 350 351 SValBuilder &svalBuilder = C.getSValBuilder(); 352 ASTContext &Ctx = svalBuilder.getContext(); 353 const LocationContext *LCtx = C.getLocationContext(); 354 355 QualType sizeTy = Size->getType(); 356 QualType PtrTy = Ctx.getPointerType(Ctx.CharTy); 357 358 // Check that the first buffer is non-null. 359 SVal BufVal = state->getSVal(FirstBuf, LCtx); 360 state = checkNonNull(C, state, FirstBuf, BufVal); 361 if (!state) 362 return NULL; 363 364 // If out-of-bounds checking is turned off, skip the rest. 365 if (!Filter.CheckCStringOutOfBounds) 366 return state; 367 368 // Get the access length and make sure it is known. 369 // FIXME: This assumes the caller has already checked that the access length 370 // is positive. And that it's unsigned. 371 SVal LengthVal = state->getSVal(Size, LCtx); 372 NonLoc *Length = dyn_cast<NonLoc>(&LengthVal); 373 if (!Length) 374 return state; 375 376 // Compute the offset of the last element to be accessed: size-1. 377 NonLoc One = cast<NonLoc>(svalBuilder.makeIntVal(1, sizeTy)); 378 NonLoc LastOffset = cast<NonLoc>(svalBuilder.evalBinOpNN(state, BO_Sub, 379 *Length, One, sizeTy)); 380 381 // Check that the first buffer is sufficiently long. 382 SVal BufStart = svalBuilder.evalCast(BufVal, PtrTy, FirstBuf->getType()); 383 if (Loc *BufLoc = dyn_cast<Loc>(&BufStart)) { 384 const Expr *warningExpr = (WarnAboutSize ? Size : FirstBuf); 385 386 SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc, 387 LastOffset, PtrTy); 388 state = CheckLocation(C, state, warningExpr, BufEnd, firstMessage); 389 390 // If the buffer isn't large enough, abort. 391 if (!state) 392 return NULL; 393 } 394 395 // If there's a second buffer, check it as well. 396 if (SecondBuf) { 397 BufVal = state->getSVal(SecondBuf, LCtx); 398 state = checkNonNull(C, state, SecondBuf, BufVal); 399 if (!state) 400 return NULL; 401 402 BufStart = svalBuilder.evalCast(BufVal, PtrTy, SecondBuf->getType()); 403 if (Loc *BufLoc = dyn_cast<Loc>(&BufStart)) { 404 const Expr *warningExpr = (WarnAboutSize ? Size : SecondBuf); 405 406 SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc, 407 LastOffset, PtrTy); 408 state = CheckLocation(C, state, warningExpr, BufEnd, secondMessage); 409 } 410 } 411 412 // Large enough or not, return this state! 413 return state; 414} 415 416ProgramStateRef CStringChecker::CheckOverlap(CheckerContext &C, 417 ProgramStateRef state, 418 const Expr *Size, 419 const Expr *First, 420 const Expr *Second) const { 421 if (!Filter.CheckCStringBufferOverlap) 422 return state; 423 424 // Do a simple check for overlap: if the two arguments are from the same 425 // buffer, see if the end of the first is greater than the start of the second 426 // or vice versa. 427 428 // If a previous check has failed, propagate the failure. 429 if (!state) 430 return NULL; 431 432 ProgramStateRef stateTrue, stateFalse; 433 434 // Get the buffer values and make sure they're known locations. 435 const LocationContext *LCtx = C.getLocationContext(); 436 SVal firstVal = state->getSVal(First, LCtx); 437 SVal secondVal = state->getSVal(Second, LCtx); 438 439 Loc *firstLoc = dyn_cast<Loc>(&firstVal); 440 if (!firstLoc) 441 return state; 442 443 Loc *secondLoc = dyn_cast<Loc>(&secondVal); 444 if (!secondLoc) 445 return state; 446 447 // Are the two values the same? 448 SValBuilder &svalBuilder = C.getSValBuilder(); 449 llvm::tie(stateTrue, stateFalse) = 450 state->assume(svalBuilder.evalEQ(state, *firstLoc, *secondLoc)); 451 452 if (stateTrue && !stateFalse) { 453 // If the values are known to be equal, that's automatically an overlap. 454 emitOverlapBug(C, stateTrue, First, Second); 455 return NULL; 456 } 457 458 // assume the two expressions are not equal. 459 assert(stateFalse); 460 state = stateFalse; 461 462 // Which value comes first? 463 QualType cmpTy = svalBuilder.getConditionType(); 464 SVal reverse = svalBuilder.evalBinOpLL(state, BO_GT, 465 *firstLoc, *secondLoc, cmpTy); 466 DefinedOrUnknownSVal *reverseTest = dyn_cast<DefinedOrUnknownSVal>(&reverse); 467 if (!reverseTest) 468 return state; 469 470 llvm::tie(stateTrue, stateFalse) = state->assume(*reverseTest); 471 if (stateTrue) { 472 if (stateFalse) { 473 // If we don't know which one comes first, we can't perform this test. 474 return state; 475 } else { 476 // Switch the values so that firstVal is before secondVal. 477 Loc *tmpLoc = firstLoc; 478 firstLoc = secondLoc; 479 secondLoc = tmpLoc; 480 481 // Switch the Exprs as well, so that they still correspond. 482 const Expr *tmpExpr = First; 483 First = Second; 484 Second = tmpExpr; 485 } 486 } 487 488 // Get the length, and make sure it too is known. 489 SVal LengthVal = state->getSVal(Size, LCtx); 490 NonLoc *Length = dyn_cast<NonLoc>(&LengthVal); 491 if (!Length) 492 return state; 493 494 // Convert the first buffer's start address to char*. 495 // Bail out if the cast fails. 496 ASTContext &Ctx = svalBuilder.getContext(); 497 QualType CharPtrTy = Ctx.getPointerType(Ctx.CharTy); 498 SVal FirstStart = svalBuilder.evalCast(*firstLoc, CharPtrTy, 499 First->getType()); 500 Loc *FirstStartLoc = dyn_cast<Loc>(&FirstStart); 501 if (!FirstStartLoc) 502 return state; 503 504 // Compute the end of the first buffer. Bail out if THAT fails. 505 SVal FirstEnd = svalBuilder.evalBinOpLN(state, BO_Add, 506 *FirstStartLoc, *Length, CharPtrTy); 507 Loc *FirstEndLoc = dyn_cast<Loc>(&FirstEnd); 508 if (!FirstEndLoc) 509 return state; 510 511 // Is the end of the first buffer past the start of the second buffer? 512 SVal Overlap = svalBuilder.evalBinOpLL(state, BO_GT, 513 *FirstEndLoc, *secondLoc, cmpTy); 514 DefinedOrUnknownSVal *OverlapTest = dyn_cast<DefinedOrUnknownSVal>(&Overlap); 515 if (!OverlapTest) 516 return state; 517 518 llvm::tie(stateTrue, stateFalse) = state->assume(*OverlapTest); 519 520 if (stateTrue && !stateFalse) { 521 // Overlap! 522 emitOverlapBug(C, stateTrue, First, Second); 523 return NULL; 524 } 525 526 // assume the two expressions don't overlap. 527 assert(stateFalse); 528 return stateFalse; 529} 530 531void CStringChecker::emitOverlapBug(CheckerContext &C, ProgramStateRef state, 532 const Stmt *First, const Stmt *Second) const { 533 ExplodedNode *N = C.generateSink(state); 534 if (!N) 535 return; 536 537 if (!BT_Overlap) 538 BT_Overlap.reset(new BugType("Unix API", "Improper arguments")); 539 540 // Generate a report for this bug. 541 BugReport *report = 542 new BugReport(*BT_Overlap, 543 "Arguments must not be overlapping buffers", N); 544 report->addRange(First->getSourceRange()); 545 report->addRange(Second->getSourceRange()); 546 547 C.EmitReport(report); 548} 549 550ProgramStateRef CStringChecker::checkAdditionOverflow(CheckerContext &C, 551 ProgramStateRef state, 552 NonLoc left, 553 NonLoc right) const { 554 // If out-of-bounds checking is turned off, skip the rest. 555 if (!Filter.CheckCStringOutOfBounds) 556 return state; 557 558 // If a previous check has failed, propagate the failure. 559 if (!state) 560 return NULL; 561 562 SValBuilder &svalBuilder = C.getSValBuilder(); 563 BasicValueFactory &BVF = svalBuilder.getBasicValueFactory(); 564 565 QualType sizeTy = svalBuilder.getContext().getSizeType(); 566 const llvm::APSInt &maxValInt = BVF.getMaxValue(sizeTy); 567 NonLoc maxVal = svalBuilder.makeIntVal(maxValInt); 568 569 SVal maxMinusRight; 570 if (isa<nonloc::ConcreteInt>(right)) { 571 maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, right, 572 sizeTy); 573 } else { 574 // Try switching the operands. (The order of these two assignments is 575 // important!) 576 maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, left, 577 sizeTy); 578 left = right; 579 } 580 581 if (NonLoc *maxMinusRightNL = dyn_cast<NonLoc>(&maxMinusRight)) { 582 QualType cmpTy = svalBuilder.getConditionType(); 583 // If left > max - right, we have an overflow. 584 SVal willOverflow = svalBuilder.evalBinOpNN(state, BO_GT, left, 585 *maxMinusRightNL, cmpTy); 586 587 ProgramStateRef stateOverflow, stateOkay; 588 llvm::tie(stateOverflow, stateOkay) = 589 state->assume(cast<DefinedOrUnknownSVal>(willOverflow)); 590 591 if (stateOverflow && !stateOkay) { 592 // We have an overflow. Emit a bug report. 593 ExplodedNode *N = C.generateSink(stateOverflow); 594 if (!N) 595 return NULL; 596 597 if (!BT_AdditionOverflow) 598 BT_AdditionOverflow.reset(new BuiltinBug("API", 599 "Sum of expressions causes overflow")); 600 601 // This isn't a great error message, but this should never occur in real 602 // code anyway -- you'd have to create a buffer longer than a size_t can 603 // represent, which is sort of a contradiction. 604 const char *warning = 605 "This expression will create a string whose length is too big to " 606 "be represented as a size_t"; 607 608 // Generate a report for this bug. 609 BugReport *report = new BugReport(*BT_AdditionOverflow, warning, N); 610 C.EmitReport(report); 611 612 return NULL; 613 } 614 615 // From now on, assume an overflow didn't occur. 616 assert(stateOkay); 617 state = stateOkay; 618 } 619 620 return state; 621} 622 623ProgramStateRef CStringChecker::setCStringLength(ProgramStateRef state, 624 const MemRegion *MR, 625 SVal strLength) { 626 assert(!strLength.isUndef() && "Attempt to set an undefined string length"); 627 628 MR = MR->StripCasts(); 629 630 switch (MR->getKind()) { 631 case MemRegion::StringRegionKind: 632 // FIXME: This can happen if we strcpy() into a string region. This is 633 // undefined [C99 6.4.5p6], but we should still warn about it. 634 return state; 635 636 case MemRegion::SymbolicRegionKind: 637 case MemRegion::AllocaRegionKind: 638 case MemRegion::VarRegionKind: 639 case MemRegion::FieldRegionKind: 640 case MemRegion::ObjCIvarRegionKind: 641 // These are the types we can currently track string lengths for. 642 break; 643 644 case MemRegion::ElementRegionKind: 645 // FIXME: Handle element regions by upper-bounding the parent region's 646 // string length. 647 return state; 648 649 default: 650 // Other regions (mostly non-data) can't have a reliable C string length. 651 // For now, just ignore the change. 652 // FIXME: These are rare but not impossible. We should output some kind of 653 // warning for things like strcpy((char[]){'a', 0}, "b"); 654 return state; 655 } 656 657 if (strLength.isUnknown()) 658 return state->remove<CStringLength>(MR); 659 660 return state->set<CStringLength>(MR, strLength); 661} 662 663SVal CStringChecker::getCStringLengthForRegion(CheckerContext &C, 664 ProgramStateRef &state, 665 const Expr *Ex, 666 const MemRegion *MR, 667 bool hypothetical) { 668 if (!hypothetical) { 669 // If there's a recorded length, go ahead and return it. 670 const SVal *Recorded = state->get<CStringLength>(MR); 671 if (Recorded) 672 return *Recorded; 673 } 674 675 // Otherwise, get a new symbol and update the state. 676 unsigned Count = C.getCurrentBlockCount(); 677 SValBuilder &svalBuilder = C.getSValBuilder(); 678 QualType sizeTy = svalBuilder.getContext().getSizeType(); 679 SVal strLength = svalBuilder.getMetadataSymbolVal(CStringChecker::getTag(), 680 MR, Ex, sizeTy, Count); 681 682 if (!hypothetical) 683 state = state->set<CStringLength>(MR, strLength); 684 685 return strLength; 686} 687 688SVal CStringChecker::getCStringLength(CheckerContext &C, ProgramStateRef &state, 689 const Expr *Ex, SVal Buf, 690 bool hypothetical) const { 691 const MemRegion *MR = Buf.getAsRegion(); 692 if (!MR) { 693 // If we can't get a region, see if it's something we /know/ isn't a 694 // C string. In the context of locations, the only time we can issue such 695 // a warning is for labels. 696 if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&Buf)) { 697 if (!Filter.CheckCStringNotNullTerm) 698 return UndefinedVal(); 699 700 if (ExplodedNode *N = C.addTransition(state)) { 701 if (!BT_NotCString) 702 BT_NotCString.reset(new BuiltinBug("Unix API", 703 "Argument is not a null-terminated string.")); 704 705 SmallString<120> buf; 706 llvm::raw_svector_ostream os(buf); 707 assert(CurrentFunctionDescription); 708 os << "Argument to " << CurrentFunctionDescription 709 << " is the address of the label '" << Label->getLabel()->getName() 710 << "', which is not a null-terminated string"; 711 712 // Generate a report for this bug. 713 BugReport *report = new BugReport(*BT_NotCString, 714 os.str(), N); 715 716 report->addRange(Ex->getSourceRange()); 717 C.EmitReport(report); 718 } 719 return UndefinedVal(); 720 721 } 722 723 // If it's not a region and not a label, give up. 724 return UnknownVal(); 725 } 726 727 // If we have a region, strip casts from it and see if we can figure out 728 // its length. For anything we can't figure out, just return UnknownVal. 729 MR = MR->StripCasts(); 730 731 switch (MR->getKind()) { 732 case MemRegion::StringRegionKind: { 733 // Modifying the contents of string regions is undefined [C99 6.4.5p6], 734 // so we can assume that the byte length is the correct C string length. 735 SValBuilder &svalBuilder = C.getSValBuilder(); 736 QualType sizeTy = svalBuilder.getContext().getSizeType(); 737 const StringLiteral *strLit = cast<StringRegion>(MR)->getStringLiteral(); 738 return svalBuilder.makeIntVal(strLit->getByteLength(), sizeTy); 739 } 740 case MemRegion::SymbolicRegionKind: 741 case MemRegion::AllocaRegionKind: 742 case MemRegion::VarRegionKind: 743 case MemRegion::FieldRegionKind: 744 case MemRegion::ObjCIvarRegionKind: 745 return getCStringLengthForRegion(C, state, Ex, MR, hypothetical); 746 case MemRegion::CompoundLiteralRegionKind: 747 // FIXME: Can we track this? Is it necessary? 748 return UnknownVal(); 749 case MemRegion::ElementRegionKind: 750 // FIXME: How can we handle this? It's not good enough to subtract the 751 // offset from the base string length; consider "123\x00567" and &a[5]. 752 return UnknownVal(); 753 default: 754 // Other regions (mostly non-data) can't have a reliable C string length. 755 // In this case, an error is emitted and UndefinedVal is returned. 756 // The caller should always be prepared to handle this case. 757 if (!Filter.CheckCStringNotNullTerm) 758 return UndefinedVal(); 759 760 if (ExplodedNode *N = C.addTransition(state)) { 761 if (!BT_NotCString) 762 BT_NotCString.reset(new BuiltinBug("Unix API", 763 "Argument is not a null-terminated string.")); 764 765 SmallString<120> buf; 766 llvm::raw_svector_ostream os(buf); 767 768 assert(CurrentFunctionDescription); 769 os << "Argument to " << CurrentFunctionDescription << " is "; 770 771 if (SummarizeRegion(os, C.getASTContext(), MR)) 772 os << ", which is not a null-terminated string"; 773 else 774 os << "not a null-terminated string"; 775 776 // Generate a report for this bug. 777 BugReport *report = new BugReport(*BT_NotCString, 778 os.str(), N); 779 780 report->addRange(Ex->getSourceRange()); 781 C.EmitReport(report); 782 } 783 784 return UndefinedVal(); 785 } 786} 787 788const StringLiteral *CStringChecker::getCStringLiteral(CheckerContext &C, 789 ProgramStateRef &state, const Expr *expr, SVal val) const { 790 791 // Get the memory region pointed to by the val. 792 const MemRegion *bufRegion = val.getAsRegion(); 793 if (!bufRegion) 794 return NULL; 795 796 // Strip casts off the memory region. 797 bufRegion = bufRegion->StripCasts(); 798 799 // Cast the memory region to a string region. 800 const StringRegion *strRegion= dyn_cast<StringRegion>(bufRegion); 801 if (!strRegion) 802 return NULL; 803 804 // Return the actual string in the string region. 805 return strRegion->getStringLiteral(); 806} 807 808ProgramStateRef CStringChecker::InvalidateBuffer(CheckerContext &C, 809 ProgramStateRef state, 810 const Expr *E, SVal V) { 811 Loc *L = dyn_cast<Loc>(&V); 812 if (!L) 813 return state; 814 815 // FIXME: This is a simplified version of what's in CFRefCount.cpp -- it makes 816 // some assumptions about the value that CFRefCount can't. Even so, it should 817 // probably be refactored. 818 if (loc::MemRegionVal* MR = dyn_cast<loc::MemRegionVal>(L)) { 819 const MemRegion *R = MR->getRegion()->StripCasts(); 820 821 // Are we dealing with an ElementRegion? If so, we should be invalidating 822 // the super-region. 823 if (const ElementRegion *ER = dyn_cast<ElementRegion>(R)) { 824 R = ER->getSuperRegion(); 825 // FIXME: What about layers of ElementRegions? 826 } 827 828 // Invalidate this region. 829 unsigned Count = C.getCurrentBlockCount(); 830 const LocationContext *LCtx = C.getPredecessor()->getLocationContext(); 831 return state->invalidateRegions(R, E, Count, LCtx); 832 } 833 834 // If we have a non-region value by chance, just remove the binding. 835 // FIXME: is this necessary or correct? This handles the non-Region 836 // cases. Is it ever valid to store to these? 837 return state->unbindLoc(*L); 838} 839 840bool CStringChecker::SummarizeRegion(raw_ostream &os, ASTContext &Ctx, 841 const MemRegion *MR) { 842 const TypedValueRegion *TVR = dyn_cast<TypedValueRegion>(MR); 843 844 switch (MR->getKind()) { 845 case MemRegion::FunctionTextRegionKind: { 846 const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl(); 847 if (FD) 848 os << "the address of the function '" << *FD << '\''; 849 else 850 os << "the address of a function"; 851 return true; 852 } 853 case MemRegion::BlockTextRegionKind: 854 os << "block text"; 855 return true; 856 case MemRegion::BlockDataRegionKind: 857 os << "a block"; 858 return true; 859 case MemRegion::CXXThisRegionKind: 860 case MemRegion::CXXTempObjectRegionKind: 861 os << "a C++ temp object of type " << TVR->getValueType().getAsString(); 862 return true; 863 case MemRegion::VarRegionKind: 864 os << "a variable of type" << TVR->getValueType().getAsString(); 865 return true; 866 case MemRegion::FieldRegionKind: 867 os << "a field of type " << TVR->getValueType().getAsString(); 868 return true; 869 case MemRegion::ObjCIvarRegionKind: 870 os << "an instance variable of type " << TVR->getValueType().getAsString(); 871 return true; 872 default: 873 return false; 874 } 875} 876 877//===----------------------------------------------------------------------===// 878// evaluation of individual function calls. 879//===----------------------------------------------------------------------===// 880 881void CStringChecker::evalCopyCommon(CheckerContext &C, 882 const CallExpr *CE, 883 ProgramStateRef state, 884 const Expr *Size, const Expr *Dest, 885 const Expr *Source, bool Restricted, 886 bool IsMempcpy) const { 887 CurrentFunctionDescription = "memory copy function"; 888 889 // See if the size argument is zero. 890 const LocationContext *LCtx = C.getLocationContext(); 891 SVal sizeVal = state->getSVal(Size, LCtx); 892 QualType sizeTy = Size->getType(); 893 894 ProgramStateRef stateZeroSize, stateNonZeroSize; 895 llvm::tie(stateZeroSize, stateNonZeroSize) = 896 assumeZero(C, state, sizeVal, sizeTy); 897 898 // Get the value of the Dest. 899 SVal destVal = state->getSVal(Dest, LCtx); 900 901 // If the size is zero, there won't be any actual memory access, so 902 // just bind the return value to the destination buffer and return. 903 if (stateZeroSize && !stateNonZeroSize) { 904 stateZeroSize = stateZeroSize->BindExpr(CE, LCtx, destVal); 905 C.addTransition(stateZeroSize); 906 return; 907 } 908 909 // If the size can be nonzero, we have to check the other arguments. 910 if (stateNonZeroSize) { 911 state = stateNonZeroSize; 912 913 // Ensure the destination is not null. If it is NULL there will be a 914 // NULL pointer dereference. 915 state = checkNonNull(C, state, Dest, destVal); 916 if (!state) 917 return; 918 919 // Get the value of the Src. 920 SVal srcVal = state->getSVal(Source, LCtx); 921 922 // Ensure the source is not null. If it is NULL there will be a 923 // NULL pointer dereference. 924 state = checkNonNull(C, state, Source, srcVal); 925 if (!state) 926 return; 927 928 // Ensure the accesses are valid and that the buffers do not overlap. 929 const char * const writeWarning = 930 "Memory copy function overflows destination buffer"; 931 state = CheckBufferAccess(C, state, Size, Dest, Source, 932 writeWarning, /* sourceWarning = */ NULL); 933 if (Restricted) 934 state = CheckOverlap(C, state, Size, Dest, Source); 935 936 if (!state) 937 return; 938 939 // If this is mempcpy, get the byte after the last byte copied and 940 // bind the expr. 941 if (IsMempcpy) { 942 loc::MemRegionVal *destRegVal = dyn_cast<loc::MemRegionVal>(&destVal); 943 assert(destRegVal && "Destination should be a known MemRegionVal here"); 944 945 // Get the length to copy. 946 NonLoc *lenValNonLoc = dyn_cast<NonLoc>(&sizeVal); 947 948 if (lenValNonLoc) { 949 // Get the byte after the last byte copied. 950 SVal lastElement = C.getSValBuilder().evalBinOpLN(state, BO_Add, 951 *destRegVal, 952 *lenValNonLoc, 953 Dest->getType()); 954 955 // The byte after the last byte copied is the return value. 956 state = state->BindExpr(CE, LCtx, lastElement); 957 } else { 958 // If we don't know how much we copied, we can at least 959 // conjure a return value for later. 960 unsigned Count = C.getCurrentBlockCount(); 961 SVal result = 962 C.getSValBuilder().getConjuredSymbolVal(NULL, CE, LCtx, Count); 963 state = state->BindExpr(CE, LCtx, result); 964 } 965 966 } else { 967 // All other copies return the destination buffer. 968 // (Well, bcopy() has a void return type, but this won't hurt.) 969 state = state->BindExpr(CE, LCtx, destVal); 970 } 971 972 // Invalidate the destination. 973 // FIXME: Even if we can't perfectly model the copy, we should see if we 974 // can use LazyCompoundVals to copy the source values into the destination. 975 // This would probably remove any existing bindings past the end of the 976 // copied region, but that's still an improvement over blank invalidation. 977 state = InvalidateBuffer(C, state, Dest, 978 state->getSVal(Dest, C.getLocationContext())); 979 C.addTransition(state); 980 } 981} 982 983 984void CStringChecker::evalMemcpy(CheckerContext &C, const CallExpr *CE) const { 985 if (CE->getNumArgs() < 3) 986 return; 987 988 // void *memcpy(void *restrict dst, const void *restrict src, size_t n); 989 // The return value is the address of the destination buffer. 990 const Expr *Dest = CE->getArg(0); 991 ProgramStateRef state = C.getState(); 992 993 evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true); 994} 995 996void CStringChecker::evalMempcpy(CheckerContext &C, const CallExpr *CE) const { 997 if (CE->getNumArgs() < 3) 998 return; 999 1000 // void *mempcpy(void *restrict dst, const void *restrict src, size_t n); 1001 // The return value is a pointer to the byte following the last written byte. 1002 const Expr *Dest = CE->getArg(0); 1003 ProgramStateRef state = C.getState(); 1004 1005 evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true, true); 1006} 1007 1008void CStringChecker::evalMemmove(CheckerContext &C, const CallExpr *CE) const { 1009 if (CE->getNumArgs() < 3) 1010 return; 1011 1012 // void *memmove(void *dst, const void *src, size_t n); 1013 // The return value is the address of the destination buffer. 1014 const Expr *Dest = CE->getArg(0); 1015 ProgramStateRef state = C.getState(); 1016 1017 evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1)); 1018} 1019 1020void CStringChecker::evalBcopy(CheckerContext &C, const CallExpr *CE) const { 1021 if (CE->getNumArgs() < 3) 1022 return; 1023 1024 // void bcopy(const void *src, void *dst, size_t n); 1025 evalCopyCommon(C, CE, C.getState(), 1026 CE->getArg(2), CE->getArg(1), CE->getArg(0)); 1027} 1028 1029void CStringChecker::evalMemcmp(CheckerContext &C, const CallExpr *CE) const { 1030 if (CE->getNumArgs() < 3) 1031 return; 1032 1033 // int memcmp(const void *s1, const void *s2, size_t n); 1034 CurrentFunctionDescription = "memory comparison function"; 1035 1036 const Expr *Left = CE->getArg(0); 1037 const Expr *Right = CE->getArg(1); 1038 const Expr *Size = CE->getArg(2); 1039 1040 ProgramStateRef state = C.getState(); 1041 SValBuilder &svalBuilder = C.getSValBuilder(); 1042 1043 // See if the size argument is zero. 1044 const LocationContext *LCtx = C.getLocationContext(); 1045 SVal sizeVal = state->getSVal(Size, LCtx); 1046 QualType sizeTy = Size->getType(); 1047 1048 ProgramStateRef stateZeroSize, stateNonZeroSize; 1049 llvm::tie(stateZeroSize, stateNonZeroSize) = 1050 assumeZero(C, state, sizeVal, sizeTy); 1051 1052 // If the size can be zero, the result will be 0 in that case, and we don't 1053 // have to check either of the buffers. 1054 if (stateZeroSize) { 1055 state = stateZeroSize; 1056 state = state->BindExpr(CE, LCtx, 1057 svalBuilder.makeZeroVal(CE->getType())); 1058 C.addTransition(state); 1059 } 1060 1061 // If the size can be nonzero, we have to check the other arguments. 1062 if (stateNonZeroSize) { 1063 state = stateNonZeroSize; 1064 // If we know the two buffers are the same, we know the result is 0. 1065 // First, get the two buffers' addresses. Another checker will have already 1066 // made sure they're not undefined. 1067 DefinedOrUnknownSVal LV = 1068 cast<DefinedOrUnknownSVal>(state->getSVal(Left, LCtx)); 1069 DefinedOrUnknownSVal RV = 1070 cast<DefinedOrUnknownSVal>(state->getSVal(Right, LCtx)); 1071 1072 // See if they are the same. 1073 DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV); 1074 ProgramStateRef StSameBuf, StNotSameBuf; 1075 llvm::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf); 1076 1077 // If the two arguments might be the same buffer, we know the result is 0, 1078 // and we only need to check one size. 1079 if (StSameBuf) { 1080 state = StSameBuf; 1081 state = CheckBufferAccess(C, state, Size, Left); 1082 if (state) { 1083 state = StSameBuf->BindExpr(CE, LCtx, 1084 svalBuilder.makeZeroVal(CE->getType())); 1085 C.addTransition(state); 1086 } 1087 } 1088 1089 // If the two arguments might be different buffers, we have to check the 1090 // size of both of them. 1091 if (StNotSameBuf) { 1092 state = StNotSameBuf; 1093 state = CheckBufferAccess(C, state, Size, Left, Right); 1094 if (state) { 1095 // The return value is the comparison result, which we don't know. 1096 unsigned Count = C.getCurrentBlockCount(); 1097 SVal CmpV = svalBuilder.getConjuredSymbolVal(NULL, CE, LCtx, Count); 1098 state = state->BindExpr(CE, LCtx, CmpV); 1099 C.addTransition(state); 1100 } 1101 } 1102 } 1103} 1104 1105void CStringChecker::evalstrLength(CheckerContext &C, 1106 const CallExpr *CE) const { 1107 if (CE->getNumArgs() < 1) 1108 return; 1109 1110 // size_t strlen(const char *s); 1111 evalstrLengthCommon(C, CE, /* IsStrnlen = */ false); 1112} 1113 1114void CStringChecker::evalstrnLength(CheckerContext &C, 1115 const CallExpr *CE) const { 1116 if (CE->getNumArgs() < 2) 1117 return; 1118 1119 // size_t strnlen(const char *s, size_t maxlen); 1120 evalstrLengthCommon(C, CE, /* IsStrnlen = */ true); 1121} 1122 1123void CStringChecker::evalstrLengthCommon(CheckerContext &C, const CallExpr *CE, 1124 bool IsStrnlen) const { 1125 CurrentFunctionDescription = "string length function"; 1126 ProgramStateRef state = C.getState(); 1127 const LocationContext *LCtx = C.getLocationContext(); 1128 1129 if (IsStrnlen) { 1130 const Expr *maxlenExpr = CE->getArg(1); 1131 SVal maxlenVal = state->getSVal(maxlenExpr, LCtx); 1132 1133 ProgramStateRef stateZeroSize, stateNonZeroSize; 1134 llvm::tie(stateZeroSize, stateNonZeroSize) = 1135 assumeZero(C, state, maxlenVal, maxlenExpr->getType()); 1136 1137 // If the size can be zero, the result will be 0 in that case, and we don't 1138 // have to check the string itself. 1139 if (stateZeroSize) { 1140 SVal zero = C.getSValBuilder().makeZeroVal(CE->getType()); 1141 stateZeroSize = stateZeroSize->BindExpr(CE, LCtx, zero); 1142 C.addTransition(stateZeroSize); 1143 } 1144 1145 // If the size is GUARANTEED to be zero, we're done! 1146 if (!stateNonZeroSize) 1147 return; 1148 1149 // Otherwise, record the assumption that the size is nonzero. 1150 state = stateNonZeroSize; 1151 } 1152 1153 // Check that the string argument is non-null. 1154 const Expr *Arg = CE->getArg(0); 1155 SVal ArgVal = state->getSVal(Arg, LCtx); 1156 1157 state = checkNonNull(C, state, Arg, ArgVal); 1158 1159 if (!state) 1160 return; 1161 1162 SVal strLength = getCStringLength(C, state, Arg, ArgVal); 1163 1164 // If the argument isn't a valid C string, there's no valid state to 1165 // transition to. 1166 if (strLength.isUndef()) 1167 return; 1168 1169 DefinedOrUnknownSVal result = UnknownVal(); 1170 1171 // If the check is for strnlen() then bind the return value to no more than 1172 // the maxlen value. 1173 if (IsStrnlen) { 1174 QualType cmpTy = C.getSValBuilder().getConditionType(); 1175 1176 // It's a little unfortunate to be getting this again, 1177 // but it's not that expensive... 1178 const Expr *maxlenExpr = CE->getArg(1); 1179 SVal maxlenVal = state->getSVal(maxlenExpr, LCtx); 1180 1181 NonLoc *strLengthNL = dyn_cast<NonLoc>(&strLength); 1182 NonLoc *maxlenValNL = dyn_cast<NonLoc>(&maxlenVal); 1183 1184 if (strLengthNL && maxlenValNL) { 1185 ProgramStateRef stateStringTooLong, stateStringNotTooLong; 1186 1187 // Check if the strLength is greater than the maxlen. 1188 llvm::tie(stateStringTooLong, stateStringNotTooLong) = 1189 state->assume(cast<DefinedOrUnknownSVal> 1190 (C.getSValBuilder().evalBinOpNN(state, BO_GT, 1191 *strLengthNL, 1192 *maxlenValNL, 1193 cmpTy))); 1194 1195 if (stateStringTooLong && !stateStringNotTooLong) { 1196 // If the string is longer than maxlen, return maxlen. 1197 result = *maxlenValNL; 1198 } else if (stateStringNotTooLong && !stateStringTooLong) { 1199 // If the string is shorter than maxlen, return its length. 1200 result = *strLengthNL; 1201 } 1202 } 1203 1204 if (result.isUnknown()) { 1205 // If we don't have enough information for a comparison, there's 1206 // no guarantee the full string length will actually be returned. 1207 // All we know is the return value is the min of the string length 1208 // and the limit. This is better than nothing. 1209 unsigned Count = C.getCurrentBlockCount(); 1210 result = C.getSValBuilder().getConjuredSymbolVal(NULL, CE, LCtx, Count); 1211 NonLoc *resultNL = cast<NonLoc>(&result); 1212 1213 if (strLengthNL) { 1214 state = state->assume(cast<DefinedOrUnknownSVal> 1215 (C.getSValBuilder().evalBinOpNN(state, BO_LE, 1216 *resultNL, 1217 *strLengthNL, 1218 cmpTy)), true); 1219 } 1220 1221 if (maxlenValNL) { 1222 state = state->assume(cast<DefinedOrUnknownSVal> 1223 (C.getSValBuilder().evalBinOpNN(state, BO_LE, 1224 *resultNL, 1225 *maxlenValNL, 1226 cmpTy)), true); 1227 } 1228 } 1229 1230 } else { 1231 // This is a plain strlen(), not strnlen(). 1232 result = cast<DefinedOrUnknownSVal>(strLength); 1233 1234 // If we don't know the length of the string, conjure a return 1235 // value, so it can be used in constraints, at least. 1236 if (result.isUnknown()) { 1237 unsigned Count = C.getCurrentBlockCount(); 1238 result = C.getSValBuilder().getConjuredSymbolVal(NULL, CE, LCtx, Count); 1239 } 1240 } 1241 1242 // Bind the return value. 1243 assert(!result.isUnknown() && "Should have conjured a value by now"); 1244 state = state->BindExpr(CE, LCtx, result); 1245 C.addTransition(state); 1246} 1247 1248void CStringChecker::evalStrcpy(CheckerContext &C, const CallExpr *CE) const { 1249 if (CE->getNumArgs() < 2) 1250 return; 1251 1252 // char *strcpy(char *restrict dst, const char *restrict src); 1253 evalStrcpyCommon(C, CE, 1254 /* returnEnd = */ false, 1255 /* isBounded = */ false, 1256 /* isAppending = */ false); 1257} 1258 1259void CStringChecker::evalStrncpy(CheckerContext &C, const CallExpr *CE) const { 1260 if (CE->getNumArgs() < 3) 1261 return; 1262 1263 // char *strncpy(char *restrict dst, const char *restrict src, size_t n); 1264 evalStrcpyCommon(C, CE, 1265 /* returnEnd = */ false, 1266 /* isBounded = */ true, 1267 /* isAppending = */ false); 1268} 1269 1270void CStringChecker::evalStpcpy(CheckerContext &C, const CallExpr *CE) const { 1271 if (CE->getNumArgs() < 2) 1272 return; 1273 1274 // char *stpcpy(char *restrict dst, const char *restrict src); 1275 evalStrcpyCommon(C, CE, 1276 /* returnEnd = */ true, 1277 /* isBounded = */ false, 1278 /* isAppending = */ false); 1279} 1280 1281void CStringChecker::evalStrcat(CheckerContext &C, const CallExpr *CE) const { 1282 if (CE->getNumArgs() < 2) 1283 return; 1284 1285 //char *strcat(char *restrict s1, const char *restrict s2); 1286 evalStrcpyCommon(C, CE, 1287 /* returnEnd = */ false, 1288 /* isBounded = */ false, 1289 /* isAppending = */ true); 1290} 1291 1292void CStringChecker::evalStrncat(CheckerContext &C, const CallExpr *CE) const { 1293 if (CE->getNumArgs() < 3) 1294 return; 1295 1296 //char *strncat(char *restrict s1, const char *restrict s2, size_t n); 1297 evalStrcpyCommon(C, CE, 1298 /* returnEnd = */ false, 1299 /* isBounded = */ true, 1300 /* isAppending = */ true); 1301} 1302 1303void CStringChecker::evalStrcpyCommon(CheckerContext &C, const CallExpr *CE, 1304 bool returnEnd, bool isBounded, 1305 bool isAppending) const { 1306 CurrentFunctionDescription = "string copy function"; 1307 ProgramStateRef state = C.getState(); 1308 const LocationContext *LCtx = C.getLocationContext(); 1309 1310 // Check that the destination is non-null. 1311 const Expr *Dst = CE->getArg(0); 1312 SVal DstVal = state->getSVal(Dst, LCtx); 1313 1314 state = checkNonNull(C, state, Dst, DstVal); 1315 if (!state) 1316 return; 1317 1318 // Check that the source is non-null. 1319 const Expr *srcExpr = CE->getArg(1); 1320 SVal srcVal = state->getSVal(srcExpr, LCtx); 1321 state = checkNonNull(C, state, srcExpr, srcVal); 1322 if (!state) 1323 return; 1324 1325 // Get the string length of the source. 1326 SVal strLength = getCStringLength(C, state, srcExpr, srcVal); 1327 1328 // If the source isn't a valid C string, give up. 1329 if (strLength.isUndef()) 1330 return; 1331 1332 SValBuilder &svalBuilder = C.getSValBuilder(); 1333 QualType cmpTy = svalBuilder.getConditionType(); 1334 QualType sizeTy = svalBuilder.getContext().getSizeType(); 1335 1336 // These two values allow checking two kinds of errors: 1337 // - actual overflows caused by a source that doesn't fit in the destination 1338 // - potential overflows caused by a bound that could exceed the destination 1339 SVal amountCopied = UnknownVal(); 1340 SVal maxLastElementIndex = UnknownVal(); 1341 const char *boundWarning = NULL; 1342 1343 // If the function is strncpy, strncat, etc... it is bounded. 1344 if (isBounded) { 1345 // Get the max number of characters to copy. 1346 const Expr *lenExpr = CE->getArg(2); 1347 SVal lenVal = state->getSVal(lenExpr, LCtx); 1348 1349 // Protect against misdeclared strncpy(). 1350 lenVal = svalBuilder.evalCast(lenVal, sizeTy, lenExpr->getType()); 1351 1352 NonLoc *strLengthNL = dyn_cast<NonLoc>(&strLength); 1353 NonLoc *lenValNL = dyn_cast<NonLoc>(&lenVal); 1354 1355 // If we know both values, we might be able to figure out how much 1356 // we're copying. 1357 if (strLengthNL && lenValNL) { 1358 ProgramStateRef stateSourceTooLong, stateSourceNotTooLong; 1359 1360 // Check if the max number to copy is less than the length of the src. 1361 // If the bound is equal to the source length, strncpy won't null- 1362 // terminate the result! 1363 llvm::tie(stateSourceTooLong, stateSourceNotTooLong) = 1364 state->assume(cast<DefinedOrUnknownSVal> 1365 (svalBuilder.evalBinOpNN(state, BO_GE, *strLengthNL, 1366 *lenValNL, cmpTy))); 1367 1368 if (stateSourceTooLong && !stateSourceNotTooLong) { 1369 // Max number to copy is less than the length of the src, so the actual 1370 // strLength copied is the max number arg. 1371 state = stateSourceTooLong; 1372 amountCopied = lenVal; 1373 1374 } else if (!stateSourceTooLong && stateSourceNotTooLong) { 1375 // The source buffer entirely fits in the bound. 1376 state = stateSourceNotTooLong; 1377 amountCopied = strLength; 1378 } 1379 } 1380 1381 // We still want to know if the bound is known to be too large. 1382 if (lenValNL) { 1383 if (isAppending) { 1384 // For strncat, the check is strlen(dst) + lenVal < sizeof(dst) 1385 1386 // Get the string length of the destination. If the destination is 1387 // memory that can't have a string length, we shouldn't be copying 1388 // into it anyway. 1389 SVal dstStrLength = getCStringLength(C, state, Dst, DstVal); 1390 if (dstStrLength.isUndef()) 1391 return; 1392 1393 if (NonLoc *dstStrLengthNL = dyn_cast<NonLoc>(&dstStrLength)) { 1394 maxLastElementIndex = svalBuilder.evalBinOpNN(state, BO_Add, 1395 *lenValNL, 1396 *dstStrLengthNL, 1397 sizeTy); 1398 boundWarning = "Size argument is greater than the free space in the " 1399 "destination buffer"; 1400 } 1401 1402 } else { 1403 // For strncpy, this is just checking that lenVal <= sizeof(dst) 1404 // (Yes, strncpy and strncat differ in how they treat termination. 1405 // strncat ALWAYS terminates, but strncpy doesn't.) 1406 1407 // We need a special case for when the copy size is zero, in which 1408 // case strncpy will do no work at all. Our bounds check uses n-1 1409 // as the last element accessed, so n == 0 is problematic. 1410 ProgramStateRef StateZeroSize, StateNonZeroSize; 1411 llvm::tie(StateZeroSize, StateNonZeroSize) = 1412 assumeZero(C, state, *lenValNL, sizeTy); 1413 1414 // If the size is known to be zero, we're done. 1415 if (StateZeroSize && !StateNonZeroSize) { 1416 StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, DstVal); 1417 C.addTransition(StateZeroSize); 1418 return; 1419 } 1420 1421 // Otherwise, go ahead and figure out the last element we'll touch. 1422 // We don't record the non-zero assumption here because we can't 1423 // be sure. We won't warn on a possible zero. 1424 NonLoc one = cast<NonLoc>(svalBuilder.makeIntVal(1, sizeTy)); 1425 maxLastElementIndex = svalBuilder.evalBinOpNN(state, BO_Sub, *lenValNL, 1426 one, sizeTy); 1427 boundWarning = "Size argument is greater than the length of the " 1428 "destination buffer"; 1429 } 1430 } 1431 1432 // If we couldn't pin down the copy length, at least bound it. 1433 // FIXME: We should actually run this code path for append as well, but 1434 // right now it creates problems with constraints (since we can end up 1435 // trying to pass constraints from symbol to symbol). 1436 if (amountCopied.isUnknown() && !isAppending) { 1437 // Try to get a "hypothetical" string length symbol, which we can later 1438 // set as a real value if that turns out to be the case. 1439 amountCopied = getCStringLength(C, state, lenExpr, srcVal, true); 1440 assert(!amountCopied.isUndef()); 1441 1442 if (NonLoc *amountCopiedNL = dyn_cast<NonLoc>(&amountCopied)) { 1443 if (lenValNL) { 1444 // amountCopied <= lenVal 1445 SVal copiedLessThanBound = svalBuilder.evalBinOpNN(state, BO_LE, 1446 *amountCopiedNL, 1447 *lenValNL, 1448 cmpTy); 1449 state = state->assume(cast<DefinedOrUnknownSVal>(copiedLessThanBound), 1450 true); 1451 if (!state) 1452 return; 1453 } 1454 1455 if (strLengthNL) { 1456 // amountCopied <= strlen(source) 1457 SVal copiedLessThanSrc = svalBuilder.evalBinOpNN(state, BO_LE, 1458 *amountCopiedNL, 1459 *strLengthNL, 1460 cmpTy); 1461 state = state->assume(cast<DefinedOrUnknownSVal>(copiedLessThanSrc), 1462 true); 1463 if (!state) 1464 return; 1465 } 1466 } 1467 } 1468 1469 } else { 1470 // The function isn't bounded. The amount copied should match the length 1471 // of the source buffer. 1472 amountCopied = strLength; 1473 } 1474 1475 assert(state); 1476 1477 // This represents the number of characters copied into the destination 1478 // buffer. (It may not actually be the strlen if the destination buffer 1479 // is not terminated.) 1480 SVal finalStrLength = UnknownVal(); 1481 1482 // If this is an appending function (strcat, strncat...) then set the 1483 // string length to strlen(src) + strlen(dst) since the buffer will 1484 // ultimately contain both. 1485 if (isAppending) { 1486 // Get the string length of the destination. If the destination is memory 1487 // that can't have a string length, we shouldn't be copying into it anyway. 1488 SVal dstStrLength = getCStringLength(C, state, Dst, DstVal); 1489 if (dstStrLength.isUndef()) 1490 return; 1491 1492 NonLoc *srcStrLengthNL = dyn_cast<NonLoc>(&amountCopied); 1493 NonLoc *dstStrLengthNL = dyn_cast<NonLoc>(&dstStrLength); 1494 1495 // If we know both string lengths, we might know the final string length. 1496 if (srcStrLengthNL && dstStrLengthNL) { 1497 // Make sure the two lengths together don't overflow a size_t. 1498 state = checkAdditionOverflow(C, state, *srcStrLengthNL, *dstStrLengthNL); 1499 if (!state) 1500 return; 1501 1502 finalStrLength = svalBuilder.evalBinOpNN(state, BO_Add, *srcStrLengthNL, 1503 *dstStrLengthNL, sizeTy); 1504 } 1505 1506 // If we couldn't get a single value for the final string length, 1507 // we can at least bound it by the individual lengths. 1508 if (finalStrLength.isUnknown()) { 1509 // Try to get a "hypothetical" string length symbol, which we can later 1510 // set as a real value if that turns out to be the case. 1511 finalStrLength = getCStringLength(C, state, CE, DstVal, true); 1512 assert(!finalStrLength.isUndef()); 1513 1514 if (NonLoc *finalStrLengthNL = dyn_cast<NonLoc>(&finalStrLength)) { 1515 if (srcStrLengthNL) { 1516 // finalStrLength >= srcStrLength 1517 SVal sourceInResult = svalBuilder.evalBinOpNN(state, BO_GE, 1518 *finalStrLengthNL, 1519 *srcStrLengthNL, 1520 cmpTy); 1521 state = state->assume(cast<DefinedOrUnknownSVal>(sourceInResult), 1522 true); 1523 if (!state) 1524 return; 1525 } 1526 1527 if (dstStrLengthNL) { 1528 // finalStrLength >= dstStrLength 1529 SVal destInResult = svalBuilder.evalBinOpNN(state, BO_GE, 1530 *finalStrLengthNL, 1531 *dstStrLengthNL, 1532 cmpTy); 1533 state = state->assume(cast<DefinedOrUnknownSVal>(destInResult), 1534 true); 1535 if (!state) 1536 return; 1537 } 1538 } 1539 } 1540 1541 } else { 1542 // Otherwise, this is a copy-over function (strcpy, strncpy, ...), and 1543 // the final string length will match the input string length. 1544 finalStrLength = amountCopied; 1545 } 1546 1547 // The final result of the function will either be a pointer past the last 1548 // copied element, or a pointer to the start of the destination buffer. 1549 SVal Result = (returnEnd ? UnknownVal() : DstVal); 1550 1551 assert(state); 1552 1553 // If the destination is a MemRegion, try to check for a buffer overflow and 1554 // record the new string length. 1555 if (loc::MemRegionVal *dstRegVal = dyn_cast<loc::MemRegionVal>(&DstVal)) { 1556 QualType ptrTy = Dst->getType(); 1557 1558 // If we have an exact value on a bounded copy, use that to check for 1559 // overflows, rather than our estimate about how much is actually copied. 1560 if (boundWarning) { 1561 if (NonLoc *maxLastNL = dyn_cast<NonLoc>(&maxLastElementIndex)) { 1562 SVal maxLastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal, 1563 *maxLastNL, ptrTy); 1564 state = CheckLocation(C, state, CE->getArg(2), maxLastElement, 1565 boundWarning); 1566 if (!state) 1567 return; 1568 } 1569 } 1570 1571 // Then, if the final length is known... 1572 if (NonLoc *knownStrLength = dyn_cast<NonLoc>(&finalStrLength)) { 1573 SVal lastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal, 1574 *knownStrLength, ptrTy); 1575 1576 // ...and we haven't checked the bound, we'll check the actual copy. 1577 if (!boundWarning) { 1578 const char * const warningMsg = 1579 "String copy function overflows destination buffer"; 1580 state = CheckLocation(C, state, Dst, lastElement, warningMsg); 1581 if (!state) 1582 return; 1583 } 1584 1585 // If this is a stpcpy-style copy, the last element is the return value. 1586 if (returnEnd) 1587 Result = lastElement; 1588 } 1589 1590 // Invalidate the destination. This must happen before we set the C string 1591 // length because invalidation will clear the length. 1592 // FIXME: Even if we can't perfectly model the copy, we should see if we 1593 // can use LazyCompoundVals to copy the source values into the destination. 1594 // This would probably remove any existing bindings past the end of the 1595 // string, but that's still an improvement over blank invalidation. 1596 state = InvalidateBuffer(C, state, Dst, *dstRegVal); 1597 1598 // Set the C string length of the destination, if we know it. 1599 if (isBounded && !isAppending) { 1600 // strncpy is annoying in that it doesn't guarantee to null-terminate 1601 // the result string. If the original string didn't fit entirely inside 1602 // the bound (including the null-terminator), we don't know how long the 1603 // result is. 1604 if (amountCopied != strLength) 1605 finalStrLength = UnknownVal(); 1606 } 1607 state = setCStringLength(state, dstRegVal->getRegion(), finalStrLength); 1608 } 1609 1610 assert(state); 1611 1612 // If this is a stpcpy-style copy, but we were unable to check for a buffer 1613 // overflow, we still need a result. Conjure a return value. 1614 if (returnEnd && Result.isUnknown()) { 1615 unsigned Count = C.getCurrentBlockCount(); 1616 Result = svalBuilder.getConjuredSymbolVal(NULL, CE, LCtx, Count); 1617 } 1618 1619 // Set the return value. 1620 state = state->BindExpr(CE, LCtx, Result); 1621 C.addTransition(state); 1622} 1623 1624void CStringChecker::evalStrcmp(CheckerContext &C, const CallExpr *CE) const { 1625 if (CE->getNumArgs() < 2) 1626 return; 1627 1628 //int strcmp(const char *s1, const char *s2); 1629 evalStrcmpCommon(C, CE, /* isBounded = */ false, /* ignoreCase = */ false); 1630} 1631 1632void CStringChecker::evalStrncmp(CheckerContext &C, const CallExpr *CE) const { 1633 if (CE->getNumArgs() < 3) 1634 return; 1635 1636 //int strncmp(const char *s1, const char *s2, size_t n); 1637 evalStrcmpCommon(C, CE, /* isBounded = */ true, /* ignoreCase = */ false); 1638} 1639 1640void CStringChecker::evalStrcasecmp(CheckerContext &C, 1641 const CallExpr *CE) const { 1642 if (CE->getNumArgs() < 2) 1643 return; 1644 1645 //int strcasecmp(const char *s1, const char *s2); 1646 evalStrcmpCommon(C, CE, /* isBounded = */ false, /* ignoreCase = */ true); 1647} 1648 1649void CStringChecker::evalStrncasecmp(CheckerContext &C, 1650 const CallExpr *CE) const { 1651 if (CE->getNumArgs() < 3) 1652 return; 1653 1654 //int strncasecmp(const char *s1, const char *s2, size_t n); 1655 evalStrcmpCommon(C, CE, /* isBounded = */ true, /* ignoreCase = */ true); 1656} 1657 1658void CStringChecker::evalStrcmpCommon(CheckerContext &C, const CallExpr *CE, 1659 bool isBounded, bool ignoreCase) const { 1660 CurrentFunctionDescription = "string comparison function"; 1661 ProgramStateRef state = C.getState(); 1662 const LocationContext *LCtx = C.getLocationContext(); 1663 1664 // Check that the first string is non-null 1665 const Expr *s1 = CE->getArg(0); 1666 SVal s1Val = state->getSVal(s1, LCtx); 1667 state = checkNonNull(C, state, s1, s1Val); 1668 if (!state) 1669 return; 1670 1671 // Check that the second string is non-null. 1672 const Expr *s2 = CE->getArg(1); 1673 SVal s2Val = state->getSVal(s2, LCtx); 1674 state = checkNonNull(C, state, s2, s2Val); 1675 if (!state) 1676 return; 1677 1678 // Get the string length of the first string or give up. 1679 SVal s1Length = getCStringLength(C, state, s1, s1Val); 1680 if (s1Length.isUndef()) 1681 return; 1682 1683 // Get the string length of the second string or give up. 1684 SVal s2Length = getCStringLength(C, state, s2, s2Val); 1685 if (s2Length.isUndef()) 1686 return; 1687 1688 // If we know the two buffers are the same, we know the result is 0. 1689 // First, get the two buffers' addresses. Another checker will have already 1690 // made sure they're not undefined. 1691 DefinedOrUnknownSVal LV = cast<DefinedOrUnknownSVal>(s1Val); 1692 DefinedOrUnknownSVal RV = cast<DefinedOrUnknownSVal>(s2Val); 1693 1694 // See if they are the same. 1695 SValBuilder &svalBuilder = C.getSValBuilder(); 1696 DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV); 1697 ProgramStateRef StSameBuf, StNotSameBuf; 1698 llvm::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf); 1699 1700 // If the two arguments might be the same buffer, we know the result is 0, 1701 // and we only need to check one size. 1702 if (StSameBuf) { 1703 StSameBuf = StSameBuf->BindExpr(CE, LCtx, 1704 svalBuilder.makeZeroVal(CE->getType())); 1705 C.addTransition(StSameBuf); 1706 1707 // If the two arguments are GUARANTEED to be the same, we're done! 1708 if (!StNotSameBuf) 1709 return; 1710 } 1711 1712 assert(StNotSameBuf); 1713 state = StNotSameBuf; 1714 1715 // At this point we can go about comparing the two buffers. 1716 // For now, we only do this if they're both known string literals. 1717 1718 // Attempt to extract string literals from both expressions. 1719 const StringLiteral *s1StrLiteral = getCStringLiteral(C, state, s1, s1Val); 1720 const StringLiteral *s2StrLiteral = getCStringLiteral(C, state, s2, s2Val); 1721 bool canComputeResult = false; 1722 1723 if (s1StrLiteral && s2StrLiteral) { 1724 StringRef s1StrRef = s1StrLiteral->getString(); 1725 StringRef s2StrRef = s2StrLiteral->getString(); 1726 1727 if (isBounded) { 1728 // Get the max number of characters to compare. 1729 const Expr *lenExpr = CE->getArg(2); 1730 SVal lenVal = state->getSVal(lenExpr, LCtx); 1731 1732 // If the length is known, we can get the right substrings. 1733 if (const llvm::APSInt *len = svalBuilder.getKnownValue(state, lenVal)) { 1734 // Create substrings of each to compare the prefix. 1735 s1StrRef = s1StrRef.substr(0, (size_t)len->getZExtValue()); 1736 s2StrRef = s2StrRef.substr(0, (size_t)len->getZExtValue()); 1737 canComputeResult = true; 1738 } 1739 } else { 1740 // This is a normal, unbounded strcmp. 1741 canComputeResult = true; 1742 } 1743 1744 if (canComputeResult) { 1745 // Real strcmp stops at null characters. 1746 size_t s1Term = s1StrRef.find('\0'); 1747 if (s1Term != StringRef::npos) 1748 s1StrRef = s1StrRef.substr(0, s1Term); 1749 1750 size_t s2Term = s2StrRef.find('\0'); 1751 if (s2Term != StringRef::npos) 1752 s2StrRef = s2StrRef.substr(0, s2Term); 1753 1754 // Use StringRef's comparison methods to compute the actual result. 1755 int result; 1756 1757 if (ignoreCase) { 1758 // Compare string 1 to string 2 the same way strcasecmp() does. 1759 result = s1StrRef.compare_lower(s2StrRef); 1760 } else { 1761 // Compare string 1 to string 2 the same way strcmp() does. 1762 result = s1StrRef.compare(s2StrRef); 1763 } 1764 1765 // Build the SVal of the comparison and bind the return value. 1766 SVal resultVal = svalBuilder.makeIntVal(result, CE->getType()); 1767 state = state->BindExpr(CE, LCtx, resultVal); 1768 } 1769 } 1770 1771 if (!canComputeResult) { 1772 // Conjure a symbolic value. It's the best we can do. 1773 unsigned Count = C.getCurrentBlockCount(); 1774 SVal resultVal = svalBuilder.getConjuredSymbolVal(NULL, CE, LCtx, Count); 1775 state = state->BindExpr(CE, LCtx, resultVal); 1776 } 1777 1778 // Record this as a possible path. 1779 C.addTransition(state); 1780} 1781 1782//===----------------------------------------------------------------------===// 1783// The driver method, and other Checker callbacks. 1784//===----------------------------------------------------------------------===// 1785 1786bool CStringChecker::evalCall(const CallExpr *CE, CheckerContext &C) const { 1787 const FunctionDecl *FDecl = C.getCalleeDecl(CE); 1788 1789 if (!FDecl) 1790 return false; 1791 1792 FnCheck evalFunction = 0; 1793 if (C.isCLibraryFunction(FDecl, "memcpy")) 1794 evalFunction = &CStringChecker::evalMemcpy; 1795 else if (C.isCLibraryFunction(FDecl, "mempcpy")) 1796 evalFunction = &CStringChecker::evalMempcpy; 1797 else if (C.isCLibraryFunction(FDecl, "memcmp")) 1798 evalFunction = &CStringChecker::evalMemcmp; 1799 else if (C.isCLibraryFunction(FDecl, "memmove")) 1800 evalFunction = &CStringChecker::evalMemmove; 1801 else if (C.isCLibraryFunction(FDecl, "strcpy")) 1802 evalFunction = &CStringChecker::evalStrcpy; 1803 else if (C.isCLibraryFunction(FDecl, "strncpy")) 1804 evalFunction = &CStringChecker::evalStrncpy; 1805 else if (C.isCLibraryFunction(FDecl, "stpcpy")) 1806 evalFunction = &CStringChecker::evalStpcpy; 1807 else if (C.isCLibraryFunction(FDecl, "strcat")) 1808 evalFunction = &CStringChecker::evalStrcat; 1809 else if (C.isCLibraryFunction(FDecl, "strncat")) 1810 evalFunction = &CStringChecker::evalStrncat; 1811 else if (C.isCLibraryFunction(FDecl, "strlen")) 1812 evalFunction = &CStringChecker::evalstrLength; 1813 else if (C.isCLibraryFunction(FDecl, "strnlen")) 1814 evalFunction = &CStringChecker::evalstrnLength; 1815 else if (C.isCLibraryFunction(FDecl, "strcmp")) 1816 evalFunction = &CStringChecker::evalStrcmp; 1817 else if (C.isCLibraryFunction(FDecl, "strncmp")) 1818 evalFunction = &CStringChecker::evalStrncmp; 1819 else if (C.isCLibraryFunction(FDecl, "strcasecmp")) 1820 evalFunction = &CStringChecker::evalStrcasecmp; 1821 else if (C.isCLibraryFunction(FDecl, "strncasecmp")) 1822 evalFunction = &CStringChecker::evalStrncasecmp; 1823 else if (C.isCLibraryFunction(FDecl, "bcopy")) 1824 evalFunction = &CStringChecker::evalBcopy; 1825 else if (C.isCLibraryFunction(FDecl, "bcmp")) 1826 evalFunction = &CStringChecker::evalMemcmp; 1827 1828 // If the callee isn't a string function, let another checker handle it. 1829 if (!evalFunction) 1830 return false; 1831 1832 // Make sure each function sets its own description. 1833 // (But don't bother in a release build.) 1834 assert(!(CurrentFunctionDescription = NULL)); 1835 1836 // Check and evaluate the call. 1837 (this->*evalFunction)(C, CE); 1838 1839 // If the evaluate call resulted in no change, chain to the next eval call 1840 // handler. 1841 // Note, the custom CString evaluation calls assume that basic safety 1842 // properties are held. However, if the user chooses to turn off some of these 1843 // checks, we ignore the issues and leave the call evaluation to a generic 1844 // handler. 1845 if (!C.isDifferent()) 1846 return false; 1847 1848 return true; 1849} 1850 1851void CStringChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const { 1852 // Record string length for char a[] = "abc"; 1853 ProgramStateRef state = C.getState(); 1854 1855 for (DeclStmt::const_decl_iterator I = DS->decl_begin(), E = DS->decl_end(); 1856 I != E; ++I) { 1857 const VarDecl *D = dyn_cast<VarDecl>(*I); 1858 if (!D) 1859 continue; 1860 1861 // FIXME: Handle array fields of structs. 1862 if (!D->getType()->isArrayType()) 1863 continue; 1864 1865 const Expr *Init = D->getInit(); 1866 if (!Init) 1867 continue; 1868 if (!isa<StringLiteral>(Init)) 1869 continue; 1870 1871 Loc VarLoc = state->getLValue(D, C.getLocationContext()); 1872 const MemRegion *MR = VarLoc.getAsRegion(); 1873 if (!MR) 1874 continue; 1875 1876 SVal StrVal = state->getSVal(Init, C.getLocationContext()); 1877 assert(StrVal.isValid() && "Initializer string is unknown or undefined"); 1878 DefinedOrUnknownSVal strLength 1879 = cast<DefinedOrUnknownSVal>(getCStringLength(C, state, Init, StrVal)); 1880 1881 state = state->set<CStringLength>(MR, strLength); 1882 } 1883 1884 C.addTransition(state); 1885} 1886 1887bool CStringChecker::wantsRegionChangeUpdate(ProgramStateRef state) const { 1888 CStringLength::EntryMap Entries = state->get<CStringLength>(); 1889 return !Entries.isEmpty(); 1890} 1891 1892ProgramStateRef 1893CStringChecker::checkRegionChanges(ProgramStateRef state, 1894 const StoreManager::InvalidatedSymbols *, 1895 ArrayRef<const MemRegion *> ExplicitRegions, 1896 ArrayRef<const MemRegion *> Regions, 1897 const CallEvent *Call) const { 1898 CStringLength::EntryMap Entries = state->get<CStringLength>(); 1899 if (Entries.isEmpty()) 1900 return state; 1901 1902 llvm::SmallPtrSet<const MemRegion *, 8> Invalidated; 1903 llvm::SmallPtrSet<const MemRegion *, 32> SuperRegions; 1904 1905 // First build sets for the changed regions and their super-regions. 1906 for (ArrayRef<const MemRegion *>::iterator 1907 I = Regions.begin(), E = Regions.end(); I != E; ++I) { 1908 const MemRegion *MR = *I; 1909 Invalidated.insert(MR); 1910 1911 SuperRegions.insert(MR); 1912 while (const SubRegion *SR = dyn_cast<SubRegion>(MR)) { 1913 MR = SR->getSuperRegion(); 1914 SuperRegions.insert(MR); 1915 } 1916 } 1917 1918 CStringLength::EntryMap::Factory &F = state->get_context<CStringLength>(); 1919 1920 // Then loop over the entries in the current state. 1921 for (CStringLength::EntryMap::iterator I = Entries.begin(), 1922 E = Entries.end(); I != E; ++I) { 1923 const MemRegion *MR = I.getKey(); 1924 1925 // Is this entry for a super-region of a changed region? 1926 if (SuperRegions.count(MR)) { 1927 Entries = F.remove(Entries, MR); 1928 continue; 1929 } 1930 1931 // Is this entry for a sub-region of a changed region? 1932 const MemRegion *Super = MR; 1933 while (const SubRegion *SR = dyn_cast<SubRegion>(Super)) { 1934 Super = SR->getSuperRegion(); 1935 if (Invalidated.count(Super)) { 1936 Entries = F.remove(Entries, MR); 1937 break; 1938 } 1939 } 1940 } 1941 1942 return state->set<CStringLength>(Entries); 1943} 1944 1945void CStringChecker::checkLiveSymbols(ProgramStateRef state, 1946 SymbolReaper &SR) const { 1947 // Mark all symbols in our string length map as valid. 1948 CStringLength::EntryMap Entries = state->get<CStringLength>(); 1949 1950 for (CStringLength::EntryMap::iterator I = Entries.begin(), E = Entries.end(); 1951 I != E; ++I) { 1952 SVal Len = I.getData(); 1953 1954 for (SymExpr::symbol_iterator si = Len.symbol_begin(), 1955 se = Len.symbol_end(); si != se; ++si) 1956 SR.markInUse(*si); 1957 } 1958} 1959 1960void CStringChecker::checkDeadSymbols(SymbolReaper &SR, 1961 CheckerContext &C) const { 1962 if (!SR.hasDeadSymbols()) 1963 return; 1964 1965 ProgramStateRef state = C.getState(); 1966 CStringLength::EntryMap Entries = state->get<CStringLength>(); 1967 if (Entries.isEmpty()) 1968 return; 1969 1970 CStringLength::EntryMap::Factory &F = state->get_context<CStringLength>(); 1971 for (CStringLength::EntryMap::iterator I = Entries.begin(), E = Entries.end(); 1972 I != E; ++I) { 1973 SVal Len = I.getData(); 1974 if (SymbolRef Sym = Len.getAsSymbol()) { 1975 if (SR.isDead(Sym)) 1976 Entries = F.remove(Entries, I.getKey()); 1977 } 1978 } 1979 1980 state = state->set<CStringLength>(Entries); 1981 C.addTransition(state); 1982} 1983 1984#define REGISTER_CHECKER(name) \ 1985void ento::register##name(CheckerManager &mgr) {\ 1986 static CStringChecker *TheChecker = 0; \ 1987 if (TheChecker == 0) \ 1988 TheChecker = mgr.registerChecker<CStringChecker>(); \ 1989 TheChecker->Filter.Check##name = true; \ 1990} 1991 1992REGISTER_CHECKER(CStringNullArg) 1993REGISTER_CHECKER(CStringOutOfBounds) 1994REGISTER_CHECKER(CStringBufferOverlap) 1995REGISTER_CHECKER(CStringNotNullTerm) 1996 1997void ento::registerCStringCheckerBasic(CheckerManager &Mgr) { 1998 registerCStringNullArg(Mgr); 1999} 2000