364 lines
13 KiB
C++
364 lines
13 KiB
C++
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//= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- C++ -*-//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This defines UnixAPIChecker, which is an assortment of checks on calls
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// to various, widely used UNIX/Posix functions.
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//
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//===----------------------------------------------------------------------===//
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#include "ClangSACheckers.h"
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#include "clang/Basic/TargetInfo.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/StringSwitch.h"
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#include "llvm/Support/raw_ostream.h"
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#include <fcntl.h>
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using namespace clang;
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using namespace ento;
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namespace {
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class UnixAPIChecker : public Checker< check::PreStmt<CallExpr> > {
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mutable OwningPtr<BugType> BT_open, BT_pthreadOnce, BT_mallocZero;
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mutable Optional<uint64_t> Val_O_CREAT;
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public:
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void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
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void CheckOpen(CheckerContext &C, const CallExpr *CE) const;
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void CheckPthreadOnce(CheckerContext &C, const CallExpr *CE) const;
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void CheckCallocZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckMallocZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckReallocZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckReallocfZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const;
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typedef void (UnixAPIChecker::*SubChecker)(CheckerContext &,
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const CallExpr *) const;
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private:
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bool ReportZeroByteAllocation(CheckerContext &C,
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ProgramStateRef falseState,
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const Expr *arg,
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const char *fn_name) const;
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void BasicAllocationCheck(CheckerContext &C,
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const CallExpr *CE,
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const unsigned numArgs,
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const unsigned sizeArg,
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const char *fn) const;
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};
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} //end anonymous namespace
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//===----------------------------------------------------------------------===//
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// Utility functions.
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//===----------------------------------------------------------------------===//
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static inline void LazyInitialize(OwningPtr<BugType> &BT,
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const char *name) {
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if (BT)
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return;
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BT.reset(new BugType(name, categories::UnixAPI));
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}
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//===----------------------------------------------------------------------===//
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// "open" (man 2 open)
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//===----------------------------------------------------------------------===//
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void UnixAPIChecker::CheckOpen(CheckerContext &C, const CallExpr *CE) const {
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// The definition of O_CREAT is platform specific. We need a better way
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// of querying this information from the checking environment.
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if (!Val_O_CREAT.hasValue()) {
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if (C.getASTContext().getTargetInfo().getTriple().getVendor()
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== llvm::Triple::Apple)
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Val_O_CREAT = 0x0200;
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else {
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// FIXME: We need a more general way of getting the O_CREAT value.
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// We could possibly grovel through the preprocessor state, but
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// that would require passing the Preprocessor object to the ExprEngine.
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return;
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}
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}
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// Look at the 'oflags' argument for the O_CREAT flag.
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ProgramStateRef state = C.getState();
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if (CE->getNumArgs() < 2) {
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// The frontend should issue a warning for this case, so this is a sanity
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// check.
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return;
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}
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// Now check if oflags has O_CREAT set.
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const Expr *oflagsEx = CE->getArg(1);
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const SVal V = state->getSVal(oflagsEx, C.getLocationContext());
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if (!V.getAs<NonLoc>()) {
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// The case where 'V' can be a location can only be due to a bad header,
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// so in this case bail out.
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return;
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}
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NonLoc oflags = V.castAs<NonLoc>();
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NonLoc ocreateFlag = C.getSValBuilder()
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.makeIntVal(Val_O_CREAT.getValue(), oflagsEx->getType()).castAs<NonLoc>();
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SVal maskedFlagsUC = C.getSValBuilder().evalBinOpNN(state, BO_And,
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oflags, ocreateFlag,
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oflagsEx->getType());
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if (maskedFlagsUC.isUnknownOrUndef())
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return;
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DefinedSVal maskedFlags = maskedFlagsUC.castAs<DefinedSVal>();
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// Check if maskedFlags is non-zero.
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ProgramStateRef trueState, falseState;
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llvm::tie(trueState, falseState) = state->assume(maskedFlags);
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// Only emit an error if the value of 'maskedFlags' is properly
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// constrained;
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if (!(trueState && !falseState))
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return;
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if (CE->getNumArgs() < 3) {
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ExplodedNode *N = C.generateSink(trueState);
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if (!N)
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return;
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LazyInitialize(BT_open, "Improper use of 'open'");
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BugReport *report =
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new BugReport(*BT_open,
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"Call to 'open' requires a third argument when "
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"the 'O_CREAT' flag is set", N);
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report->addRange(oflagsEx->getSourceRange());
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C.emitReport(report);
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}
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}
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//===----------------------------------------------------------------------===//
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// pthread_once
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//===----------------------------------------------------------------------===//
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void UnixAPIChecker::CheckPthreadOnce(CheckerContext &C,
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const CallExpr *CE) const {
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// This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker.
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// They can possibly be refactored.
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if (CE->getNumArgs() < 1)
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return;
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// Check if the first argument is stack allocated. If so, issue a warning
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// because that's likely to be bad news.
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ProgramStateRef state = C.getState();
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const MemRegion *R =
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state->getSVal(CE->getArg(0), C.getLocationContext()).getAsRegion();
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if (!R || !isa<StackSpaceRegion>(R->getMemorySpace()))
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return;
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ExplodedNode *N = C.generateSink(state);
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if (!N)
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return;
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SmallString<256> S;
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llvm::raw_svector_ostream os(S);
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os << "Call to 'pthread_once' uses";
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if (const VarRegion *VR = dyn_cast<VarRegion>(R))
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os << " the local variable '" << VR->getDecl()->getName() << '\'';
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else
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os << " stack allocated memory";
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os << " for the \"control\" value. Using such transient memory for "
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"the control value is potentially dangerous.";
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if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace()))
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os << " Perhaps you intended to declare the variable as 'static'?";
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LazyInitialize(BT_pthreadOnce, "Improper use of 'pthread_once'");
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BugReport *report = new BugReport(*BT_pthreadOnce, os.str(), N);
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report->addRange(CE->getArg(0)->getSourceRange());
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C.emitReport(report);
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}
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//===----------------------------------------------------------------------===//
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// "calloc", "malloc", "realloc", "reallocf", "alloca" and "valloc"
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// with allocation size 0
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//===----------------------------------------------------------------------===//
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// FIXME: Eventually these should be rolled into the MallocChecker, but right now
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// they're more basic and valuable for widespread use.
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// Returns true if we try to do a zero byte allocation, false otherwise.
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// Fills in trueState and falseState.
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static bool IsZeroByteAllocation(ProgramStateRef state,
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const SVal argVal,
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ProgramStateRef *trueState,
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ProgramStateRef *falseState) {
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llvm::tie(*trueState, *falseState) =
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state->assume(argVal.castAs<DefinedSVal>());
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return (*falseState && !*trueState);
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}
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// Generates an error report, indicating that the function whose name is given
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// will perform a zero byte allocation.
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// Returns false if an error occured, true otherwise.
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bool UnixAPIChecker::ReportZeroByteAllocation(CheckerContext &C,
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ProgramStateRef falseState,
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const Expr *arg,
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const char *fn_name) const {
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ExplodedNode *N = C.generateSink(falseState);
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if (!N)
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return false;
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LazyInitialize(BT_mallocZero,
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"Undefined allocation of 0 bytes (CERT MEM04-C; CWE-131)");
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SmallString<256> S;
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llvm::raw_svector_ostream os(S);
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os << "Call to '" << fn_name << "' has an allocation size of 0 bytes";
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BugReport *report = new BugReport(*BT_mallocZero, os.str(), N);
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report->addRange(arg->getSourceRange());
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bugreporter::trackNullOrUndefValue(N, arg, *report);
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C.emitReport(report);
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return true;
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}
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// Does a basic check for 0-sized allocations suitable for most of the below
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// functions (modulo "calloc")
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void UnixAPIChecker::BasicAllocationCheck(CheckerContext &C,
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const CallExpr *CE,
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const unsigned numArgs,
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const unsigned sizeArg,
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const char *fn) const {
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// Sanity check for the correct number of arguments
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if (CE->getNumArgs() != numArgs)
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return;
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// Check if the allocation size is 0.
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ProgramStateRef state = C.getState();
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ProgramStateRef trueState = NULL, falseState = NULL;
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const Expr *arg = CE->getArg(sizeArg);
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SVal argVal = state->getSVal(arg, C.getLocationContext());
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if (argVal.isUnknownOrUndef())
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return;
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// Is the value perfectly constrained to zero?
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if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
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(void) ReportZeroByteAllocation(C, falseState, arg, fn);
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return;
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}
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// Assume the value is non-zero going forward.
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assert(trueState);
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if (trueState != state)
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C.addTransition(trueState);
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}
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void UnixAPIChecker::CheckCallocZero(CheckerContext &C,
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const CallExpr *CE) const {
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unsigned int nArgs = CE->getNumArgs();
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if (nArgs != 2)
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return;
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ProgramStateRef state = C.getState();
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ProgramStateRef trueState = NULL, falseState = NULL;
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unsigned int i;
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for (i = 0; i < nArgs; i++) {
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const Expr *arg = CE->getArg(i);
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SVal argVal = state->getSVal(arg, C.getLocationContext());
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if (argVal.isUnknownOrUndef()) {
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if (i == 0)
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continue;
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else
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return;
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}
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if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
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if (ReportZeroByteAllocation(C, falseState, arg, "calloc"))
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return;
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else if (i == 0)
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continue;
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else
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return;
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}
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}
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// Assume the value is non-zero going forward.
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assert(trueState);
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if (trueState != state)
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C.addTransition(trueState);
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}
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void UnixAPIChecker::CheckMallocZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 1, 0, "malloc");
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}
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void UnixAPIChecker::CheckReallocZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 2, 1, "realloc");
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}
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void UnixAPIChecker::CheckReallocfZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 2, 1, "reallocf");
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}
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void UnixAPIChecker::CheckAllocaZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 1, 0, "alloca");
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}
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void UnixAPIChecker::CheckVallocZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 1, 0, "valloc");
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}
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//===----------------------------------------------------------------------===//
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// Central dispatch function.
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//===----------------------------------------------------------------------===//
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void UnixAPIChecker::checkPreStmt(const CallExpr *CE,
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CheckerContext &C) const {
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const FunctionDecl *FD = C.getCalleeDecl(CE);
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if (!FD || FD->getKind() != Decl::Function)
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return;
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StringRef FName = C.getCalleeName(FD);
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if (FName.empty())
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return;
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SubChecker SC =
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llvm::StringSwitch<SubChecker>(FName)
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.Case("open", &UnixAPIChecker::CheckOpen)
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.Case("pthread_once", &UnixAPIChecker::CheckPthreadOnce)
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.Case("calloc", &UnixAPIChecker::CheckCallocZero)
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.Case("malloc", &UnixAPIChecker::CheckMallocZero)
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.Case("realloc", &UnixAPIChecker::CheckReallocZero)
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.Case("reallocf", &UnixAPIChecker::CheckReallocfZero)
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.Cases("alloca", "__builtin_alloca", &UnixAPIChecker::CheckAllocaZero)
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.Case("valloc", &UnixAPIChecker::CheckVallocZero)
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.Default(NULL);
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if (SC)
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(this->*SC)(C, CE);
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}
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//===----------------------------------------------------------------------===//
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// Registration.
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//===----------------------------------------------------------------------===//
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void ento::registerUnixAPIChecker(CheckerManager &mgr) {
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mgr.registerChecker<UnixAPIChecker>();
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}
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