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[Analyzer][VLASize] Support multi-dimensional arrays. 

Summary:
Check the size constraints for every (variable) dimension of the array.
Try to compute array size by multiplying size for every dimension.

Reviewers: Szelethus, martong, baloghadamsoftware, gamesh411

Reviewed By: Szelethus, martong

Subscribers: rnkovacs, xazax.hun, baloghadamsoftware, szepet, a.sidorin, mikhail.ramalho, Szelethus, donat.nagy, dkrupp, gamesh411, Charusso, martong, ASDenysPetrov, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77305
This commit is contained in:
Balázs Kéri 2020-04-14 09:20:22 +02:00
parent 99aea57928
commit 37ac1c19be
2 changed files with 149 additions and 71 deletions
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174
clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp
View File

@ -34,6 +34,9 @@ class VLASizeChecker : public Checker< check::PreStmt<DeclStmt> > {
mutable std::unique_ptr<BugType> BT;
enum VLASize_Kind { VLA_Garbage, VLA_Zero, VLA_Tainted, VLA_Negative };
ProgramStateRef checkVLASize(CheckerContext &C, ProgramStateRef State,
const Expr *SizeE) const;
void reportBug(VLASize_Kind Kind, const Expr *SizeE, ProgramStateRef State,
CheckerContext &C,
std::unique_ptr<BugReporterVisitor> Visitor = nullptr) const;
@ -43,6 +46,65 @@ public:
};
} // end anonymous namespace
ProgramStateRef VLASizeChecker::checkVLASize(CheckerContext &C,
ProgramStateRef State,
const Expr *SizeE) const {
SVal SizeV = C.getSVal(SizeE);
if (SizeV.isUndef()) {
reportBug(VLA_Garbage, SizeE, State, C);
return nullptr;
}
// See if the size value is known. It can't be undefined because we would have
// warned about that already.
if (SizeV.isUnknown())
return nullptr;
// Check if the size is tainted.
if (isTainted(State, SizeV)) {
reportBug(VLA_Tainted, SizeE, nullptr, C,
std::make_unique<TaintBugVisitor>(SizeV));
return nullptr;
}
// Check if the size is zero.
DefinedSVal SizeD = SizeV.castAs<DefinedSVal>();
ProgramStateRef StateNotZero, StateZero;
std::tie(StateNotZero, StateZero) = State->assume(SizeD);
if (StateZero && !StateNotZero) {
reportBug(VLA_Zero, SizeE, StateZero, C);
return nullptr;
}
// From this point on, assume that the size is not zero.
State = StateNotZero;
// Check if the size is negative.
SValBuilder &SVB = C.getSValBuilder();
QualType SizeTy = SizeE->getType();
DefinedOrUnknownSVal Zero = SVB.makeZeroVal(SizeTy);
SVal LessThanZeroVal = SVB.evalBinOp(State, BO_LT, SizeD, Zero, SizeTy);
if (Optional<DefinedSVal> LessThanZeroDVal =
LessThanZeroVal.getAs<DefinedSVal>()) {
ConstraintManager &CM = C.getConstraintManager();
ProgramStateRef StatePos, StateNeg;
std::tie(StateNeg, StatePos) = CM.assumeDual(State, *LessThanZeroDVal);
if (StateNeg && !StatePos) {
reportBug(VLA_Negative, SizeE, State, C); // FIXME: StateNeg ?
return nullptr;
}
State = StatePos;
}
return State;
}
void VLASizeChecker::reportBug(
VLASize_Kind Kind, const Expr *SizeE, ProgramStateRef State,
CheckerContext &C, std::unique_ptr<BugReporterVisitor> Visitor) const {
@ -89,98 +151,72 @@ void VLASizeChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const {
return;
ASTContext &Ctx = C.getASTContext();
SValBuilder &SVB = C.getSValBuilder();
ProgramStateRef State = C.getState();
const VariableArrayType *VLA = Ctx.getAsVariableArrayType(VD->getType());
if (!VLA)
return;
// FIXME: Handle multi-dimensional VLAs.
const Expr *SE = VLA->getSizeExpr();
ProgramStateRef state = C.getState();
SVal sizeV = C.getSVal(SE);
if (sizeV.isUndef()) {
reportBug(VLA_Garbage, SE, state, C);
llvm::SmallVector<const Expr *, 2> VLASizes;
const VariableArrayType *VLALast = nullptr;
// Walk over the VLAs for every dimension until a non-VLA is found.
// Collect the sizes in VLASizes, put the most inner VLA to `VLALast`.
// In "vla[x][2][y][3]" this will be the array for index "y".
// There is a VariableArrayType for every dimension (here "x", "2", "y")
// until a non-vla is found.
while (VLA) {
const Expr *SizeE = VLA->getSizeExpr();
State = checkVLASize(C, State, SizeE);
if (!State)
return;
}
// See if the size value is known. It can't be undefined because we would have
// warned about that already.
if (sizeV.isUnknown())
return;
// Check if the size is tainted.
if (isTainted(state, sizeV)) {
reportBug(VLA_Tainted, SE, nullptr, C,
std::make_unique<TaintBugVisitor>(sizeV));
return;
}
// Check if the size is zero.
DefinedSVal sizeD = sizeV.castAs<DefinedSVal>();
ProgramStateRef stateNotZero, stateZero;
std::tie(stateNotZero, stateZero) = state->assume(sizeD);
if (stateZero && !stateNotZero) {
reportBug(VLA_Zero, SE, stateZero, C);
return;
}
// From this point on, assume that the size is not zero.
state = stateNotZero;
VLASizes.push_back(SizeE);
VLALast = VLA;
VLA = Ctx.getAsVariableArrayType(VLA->getElementType());
};
assert(VLALast &&
"Array should have at least one variably-modified dimension.");
// VLASizeChecker is responsible for defining the extent of the array being
// declared. We do this by multiplying the array length by the element size,
// then matching that with the array region's extent symbol.
// Check if the size is negative.
SValBuilder &svalBuilder = C.getSValBuilder();
CanQualType SizeTy = Ctx.getSizeType();
// Get the element size.
CharUnits EleSize = Ctx.getTypeSizeInChars(VLALast->getElementType());
NonLoc ArraySize =
SVB.makeIntVal(EleSize.getQuantity(), SizeTy).castAs<NonLoc>();
QualType Ty = SE->getType();
DefinedOrUnknownSVal Zero = svalBuilder.makeZeroVal(Ty);
SVal LessThanZeroVal = svalBuilder.evalBinOp(state, BO_LT, sizeD, Zero, Ty);
if (Optional<DefinedSVal> LessThanZeroDVal =
LessThanZeroVal.getAs<DefinedSVal>()) {
ConstraintManager &CM = C.getConstraintManager();
ProgramStateRef StatePos, StateNeg;
std::tie(StateNeg, StatePos) = CM.assumeDual(state, *LessThanZeroDVal);
if (StateNeg && !StatePos) {
reportBug(VLA_Negative, SE, state, C);
for (const Expr *SizeE : VLASizes) {
auto SizeD = C.getSVal(SizeE).castAs<DefinedSVal>();
// Convert the array length to size_t.
NonLoc IndexLength =
SVB.evalCast(SizeD, SizeTy, SizeE->getType()).castAs<NonLoc>();
// Multiply the array length by the element size.
SVal Mul = SVB.evalBinOpNN(State, BO_Mul, ArraySize, IndexLength, SizeTy);
if (auto MulNonLoc = Mul.getAs<NonLoc>()) {
ArraySize = *MulNonLoc;
} else {
// Extent could not be determined.
// The state was probably still updated by the validation checks.
C.addTransition(State);
return;
}
state = StatePos;
}
// Convert the array length to size_t.
QualType SizeTy = Ctx.getSizeType();
NonLoc ArrayLength =
svalBuilder.evalCast(sizeD, SizeTy, SE->getType()).castAs<NonLoc>();
// Get the element size.
CharUnits EleSize = Ctx.getTypeSizeInChars(VLA->getElementType());
SVal EleSizeVal = svalBuilder.makeIntVal(EleSize.getQuantity(), SizeTy);
// Multiply the array length by the element size.
SVal ArraySizeVal = svalBuilder.evalBinOpNN(
state, BO_Mul, ArrayLength, EleSizeVal.castAs<NonLoc>(), SizeTy);
// Finally, assume that the array's size matches the given size.
const LocationContext *LC = C.getLocationContext();
DefinedOrUnknownSVal DynSize =
getDynamicSize(state, state->getRegion(VD, LC), svalBuilder);
getDynamicSize(State, State->getRegion(VD, LC), SVB);
DefinedOrUnknownSVal ArraySize = ArraySizeVal.castAs<DefinedOrUnknownSVal>();
DefinedOrUnknownSVal sizeIsKnown =
svalBuilder.evalEQ(state, DynSize, ArraySize);
state = state->assume(sizeIsKnown, true);
DefinedOrUnknownSVal SizeIsKnown = SVB.evalEQ(State, DynSize, ArraySize);
State = State->assume(SizeIsKnown, true);
// Assume should not fail at this point.
assert(state);
assert(State);
// Remember our assumptions!
C.addTransition(state);
C.addTransition(State);
}
void ento::registerVLASizeChecker(CheckerManager &mgr) {

44
clang/test/Analysis/vla.c
View File

@ -1,4 +1,8 @@
// RUN: %clang_analyze_cc1 -analyzer-checker=core -verify %s
// RUN: %clang_analyze_cc1 -analyzer-checker=core -analyzer-checker=debug.ExprInspection -verify %s
typedef unsigned long size_t;
size_t clang_analyzer_getExtent(void *);
void clang_analyzer_eval(int);
// Zero-sized VLAs.
void check_zero_sized_VLA(int x) {
@ -84,3 +88,41 @@ void check_negative_sized_VLA_11(int x) {
if (x > 0)
check_negative_sized_VLA_11_sub(x);
}
// Multi-dimensional arrays.
void check_zero_sized_VLA_multi1(int x) {
if (x)
return;
int vla[10][x]; // expected-warning{{Declared variable-length array (VLA) has zero size}}
}
void check_zero_sized_VLA_multi2(int x, int y) {
if (x)
return;
int vla[y][x]; // expected-warning{{Declared variable-length array (VLA) has zero size}}
}
// Check the extent.
void check_VLA_extent() {
int x = 3;
int vla1[x];
clang_analyzer_eval(clang_analyzer_getExtent(&vla1) == x * sizeof(int));
// expected-warning@-1{{TRUE}}
int vla2[x][2];
clang_analyzer_eval(clang_analyzer_getExtent(&vla2) == x * 2 * sizeof(int));
// expected-warning@-1{{TRUE}}
int vla2m[2][x];
clang_analyzer_eval(clang_analyzer_getExtent(&vla2m) == 2 * x * sizeof(int));
// expected-warning@-1{{TRUE}}
int vla3m[2][x][4];
clang_analyzer_eval(clang_analyzer_getExtent(&vla3m) == 2 * x * 4 * sizeof(int));
// expected-warning@-1{{TRUE}}
}