Author: Kashika Akhouri Date: 2025-11-21T18:51:21+05:30 New Revision: 4fca7b05e397e381466d6943a56f8407349c7594
URL: https://github.com/llvm/llvm-project/commit/4fca7b05e397e381466d6943a56f8407349c7594 DIFF: https://github.com/llvm/llvm-project/commit/4fca7b05e397e381466d6943a56f8407349c7594.diff LOG: [LifetimeSafety] Detect expiry of loans to trivially destructed types (#168855) Handling Trivially Destructed Types This PR uses `AddLifetime` to handle expiry of loans to trivially destructed types. Example: ```cpp int * trivial_uar(){ int *ptr; int x = 1; ptr = &x; return ptr; } ``` The CFG created now has an Expire Fact for trivially destructed types: ``` Function: trivial_uar Block B2: End of Block Block B1: Issue (0 (Path: x), ToOrigin: 0 (Expr: DeclRefExpr)) OriginFlow (Dest: 1 (Expr: UnaryOperator), Src: 0 (Expr: DeclRefExpr)) Use (2 (Decl: ptr), Write) OriginFlow (Dest: 2 (Decl: ptr), Src: 1 (Expr: UnaryOperator)) Use (2 (Decl: ptr), Read) OriginFlow (Dest: 3 (Expr: ImplicitCastExpr), Src: 2 (Decl: ptr)) Expire (0 (Path: x)) OriginEscapes (3 (Expr: ImplicitCastExpr)) End of Block Block B0: End of Block ``` This Expire Fact issues UAR and UAF warnings. Fixes https://github.com/llvm/llvm-project/issues/162862 Added: Modified: clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp clang/lib/Sema/AnalysisBasedWarnings.cpp clang/test/Sema/warn-lifetime-safety-dataflow.cpp clang/test/Sema/warn-lifetime-safety.cpp clang/unittests/Analysis/LifetimeSafetyTest.cpp Removed: ################################################################################ diff --git a/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h b/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h index 8ea37259c570b..878cb90b685f9 100644 --- a/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h +++ b/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h @@ -50,7 +50,7 @@ class FactsGenerator : public ConstStmtVisitor<FactsGenerator> { void VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *MTE); private: - void handleDestructor(const CFGAutomaticObjDtor &DtorOpt); + void handleLifetimeEnds(const CFGLifetimeEnds &LifetimeEnds); void handleGSLPointerConstruction(const CXXConstructExpr *CCE); diff --git a/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp b/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp index cb9a202b08968..f7be472ed15b5 100644 --- a/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp +++ b/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp @@ -63,9 +63,9 @@ void FactsGenerator::run() { const CFGElement &Element = Block->Elements[I]; if (std::optional<CFGStmt> CS = Element.getAs<CFGStmt>()) Visit(CS->getStmt()); - else if (std::optional<CFGAutomaticObjDtor> DtorOpt = - Element.getAs<CFGAutomaticObjDtor>()) - handleDestructor(*DtorOpt); + else if (std::optional<CFGLifetimeEnds> LifetimeEnds = + Element.getAs<CFGLifetimeEnds>()) + handleLifetimeEnds(*LifetimeEnds); } CurrentBlockFacts.append(EscapesInCurrentBlock.begin(), EscapesInCurrentBlock.end()); @@ -229,25 +229,19 @@ void FactsGenerator::VisitMaterializeTemporaryExpr( killAndFlowOrigin(*MTE, *MTE->getSubExpr()); } -void FactsGenerator::handleDestructor(const CFGAutomaticObjDtor &DtorOpt) { - /// TODO: Also handle trivial destructors (e.g., for `int` - /// variables) which will never have a CFGAutomaticObjDtor node. +void FactsGenerator::handleLifetimeEnds(const CFGLifetimeEnds &LifetimeEnds) { /// TODO: Handle loans to temporaries. - /// TODO: Consider using clang::CFG::BuildOptions::AddLifetime to reuse the - /// lifetime ends. - const VarDecl *DestructedVD = DtorOpt.getVarDecl(); - if (!DestructedVD) + const VarDecl *LifetimeEndsVD = LifetimeEnds.getVarDecl(); + if (!LifetimeEndsVD) return; // Iterate through all loans to see if any expire. - /// TODO(opt): Do better than a linear search to find loans associated with - /// 'DestructedVD'. - for (const Loan &L : FactMgr.getLoanMgr().getLoans()) { - const AccessPath &LoanPath = L.Path; + for (const auto &Loan : FactMgr.getLoanMgr().getLoans()) { + const AccessPath &LoanPath = Loan.Path; // Check if the loan is for a stack variable and if that variable // is the one being destructed. - if (LoanPath.D == DestructedVD) + if (LoanPath.D == LifetimeEndsVD) CurrentBlockFacts.push_back(FactMgr.createFact<ExpireFact>( - L.ID, DtorOpt.getTriggerStmt()->getEndLoc())); + Loan.ID, LifetimeEnds.getTriggerStmt()->getEndLoc())); } } diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp index 0fa75a24db4f3..43d2b9a829545 100644 --- a/clang/lib/Sema/AnalysisBasedWarnings.cpp +++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp @@ -2992,6 +2992,9 @@ void clang::sema::AnalysisBasedWarnings::IssueWarnings( bool EnableLifetimeSafetyAnalysis = S.getLangOpts().EnableLifetimeSafety; + if (EnableLifetimeSafetyAnalysis) + AC.getCFGBuildOptions().AddLifetime = true; + // Force that certain expressions appear as CFGElements in the CFG. This // is used to speed up various analyses. // FIXME: This isn't the right factoring. This is here for initial diff --git a/clang/test/Sema/warn-lifetime-safety-dataflow.cpp b/clang/test/Sema/warn-lifetime-safety-dataflow.cpp index 11d3b836db3e7..7b6fc9201af6d 100644 --- a/clang/test/Sema/warn-lifetime-safety-dataflow.cpp +++ b/clang/test/Sema/warn-lifetime-safety-dataflow.cpp @@ -59,6 +59,7 @@ int return_int_val() { int x = 10; // CHECK: Block B{{[0-9]+}}: // CHECK: Issue ([[L_X:[0-9]+]] (Path: x), ToOrigin: {{[0-9]+}} (Expr: DeclRefExpr)) +// CHECK: Expire ([[L_X:[0-9]+]] (Path: x)) return x; } // CHECK-NEXT: End of Block @@ -77,7 +78,6 @@ void loan_expires_cpp() { } -// FIXME: No expire for Trivial Destructors // CHECK-LABEL: Function: loan_expires_trivial void loan_expires_trivial() { int trivial_obj = 1; @@ -86,11 +86,29 @@ void loan_expires_trivial() { // CHECK: OriginFlow (Dest: [[O_ADDR_TRIVIAL_OBJ:[0-9]+]] (Expr: UnaryOperator), Src: [[O_DRE_TRIVIAL]] (Expr: DeclRefExpr)) int* pTrivialObj = &trivial_obj; // CHECK: OriginFlow (Dest: {{[0-9]+}} (Decl: pTrivialObj), Src: [[O_ADDR_TRIVIAL_OBJ]] (Expr: UnaryOperator)) -// CHECK-NOT: Expire +// CHECK: Expire ([[L_TRIVIAL_OBJ:[0-9]+]] (Path: trivial_obj)) // CHECK-NEXT: End of Block - // FIXME: Add check for Expire once trivial destructors are handled for expiration. } +// Trivial Destructors +// CHECK-LABEL: Function: return_int_pointer +int* return_int_pointer() { + int* ptr; +// CHECK: Block B{{[0-9]+}}: + int x = 1; +// CHECK: Issue ([[L_X:[0-9]+]] (Path: x), ToOrigin: [[O_DRE_X:[0-9]+]] (Expr: DeclRefExpr)) +// CHECK: OriginFlow (Dest: [[O_ADDR_X:[0-9]+]] (Expr: UnaryOperator), Src: [[O_DRE_X]] (Expr: DeclRefExpr)) + ptr = &x; +// CHECK: Use ([[O_PTR:[0-9]+]] (Decl: ptr), Write) +// CHECK: OriginFlow (Dest: [[O_PTR]] (Decl: ptr), Src: [[O_ADDR_X]] (Expr: UnaryOperator)) +// CHECK: Use ([[O_PTR]] (Decl: ptr), Read) +// CHECK: OriginFlow (Dest: [[O_RET_VAL:[0-9]+]] (Expr: ImplicitCastExpr), Src: [[O_PTR]] (Decl: ptr)) +// CHECK: Expire ([[L_X]] (Path: x)) +// CHECK: OriginEscapes ([[O_RET_VAL]] (Expr: ImplicitCastExpr)) + return ptr; +} +// CHECK-NEXT: End of Block + // CHECK-LABEL: Function: conditional void conditional(bool condition) { int a = 5; diff --git a/clang/test/Sema/warn-lifetime-safety.cpp b/clang/test/Sema/warn-lifetime-safety.cpp index 2803e73b5aee2..e80a05860389c 100644 --- a/clang/test/Sema/warn-lifetime-safety.cpp +++ b/clang/test/Sema/warn-lifetime-safety.cpp @@ -12,6 +12,10 @@ struct [[gsl::Pointer()]] View { void use() const; }; +class TriviallyDestructedClass { + View a, b; +}; + //===----------------------------------------------------------------------===// // Basic Definite Use-After-Free (-W...permissive) // These are cases where the pointer is guaranteed to be dangling at the use site. @@ -396,6 +400,24 @@ void loan_from_previous_iteration(MyObj safe, bool condition) { } // expected-note {{destroyed here}} } +void trivial_int_uaf() { + int * a; + { + int b = 1; + a = &b; // expected-warning {{object whose reference is captured does not live long enough}} + } // expected-note {{destroyed here}} + (void)*a; // expected-note {{later used here}} +} + +void trivial_class_uaf() { + TriviallyDestructedClass* ptr; + { + TriviallyDestructedClass s; + ptr = &s; // expected-warning {{object whose reference is captured does not live long enough}} + } // expected-note {{destroyed here}} + (void)ptr; // expected-note {{later used here}} +} + //===----------------------------------------------------------------------===// // Basic Definite Use-After-Return (Return-Stack-Address) (-W...permissive) // These are cases where the pointer is guaranteed to be dangling at the use site. @@ -493,6 +515,43 @@ MyObj& reference_return_of_local() { // expected-note@-1 {{returned here}} } +int* trivial_int_uar() { + int *a; + int b = 1; + a = &b; // expected-warning {{address of stack memory is returned later}} + return a; // expected-note {{returned here}} +} + +TriviallyDestructedClass* trivial_class_uar () { + TriviallyDestructedClass *ptr; + TriviallyDestructedClass s; + ptr = &s; // expected-warning {{address of stack memory is returned later}} + return ptr; // expected-note {{returned here}} +} + +// FIXME: No lifetime warning for this as no expire facts are generated for parameters +const int& return_parameter(int a) { + return a; +} + +// FIXME: No lifetime warning for this as no expire facts are generated for parameters +int* return_pointer_to_parameter(int a) { + return &a; +} + +const int& return_reference_to_parameter(int a) +{ + const int &b = a; + return b; // expected-warning {{address of stack memory is returned later}} + // expected-note@-1 {{returned here}} +} + +const int& get_ref_to_local() { + int a = 42; + return a; // expected-warning {{address of stack memory is returned later}} + // expected-note@-1 {{returned here}} +} + //===----------------------------------------------------------------------===// // Use-After-Scope & Use-After-Return (Return-Stack-Address) Combined // These are cases where the diagnostic kind is determined by location @@ -688,7 +747,8 @@ void lifetimebound_partial_safety(bool cond) { v.use(); // expected-note {{later used here}} } -// FIXME: Creating reference from lifetimebound call doesn't propagate loans. +// FIXME: Warning should be on the 'GetObject' call, not the assignment to 'ptr'. +// The loan from the lifetimebound argument is not propagated to the call expression itself. const MyObj& GetObject(View v [[clang::lifetimebound]]); void lifetimebound_return_reference() { View v; @@ -697,9 +757,9 @@ void lifetimebound_return_reference() { MyObj obj; View temp_v = obj; const MyObj& ref = GetObject(temp_v); - ptr = &ref; - } - (void)*ptr; + ptr = &ref; // expected-warning {{object whose reference is captured does not live long enough}} + } // expected-note {{destroyed here}} + (void)*ptr; // expected-note {{later used here}} } // FIXME: No warning for non gsl::Pointer types. Origin tracking is only supported for pointer types. diff --git a/clang/unittests/Analysis/LifetimeSafetyTest.cpp b/clang/unittests/Analysis/LifetimeSafetyTest.cpp index 558a22af72572..a895475013c98 100644 --- a/clang/unittests/Analysis/LifetimeSafetyTest.cpp +++ b/clang/unittests/Analysis/LifetimeSafetyTest.cpp @@ -59,6 +59,7 @@ class LifetimeTestRunner { BuildOptions.setAllAlwaysAdd(); BuildOptions.AddImplicitDtors = true; BuildOptions.AddTemporaryDtors = true; + BuildOptions.AddLifetime = true; // Run the main analysis. Analysis = std::make_unique<LifetimeSafetyAnalysis>(*AnalysisCtx, nullptr); @@ -1307,6 +1308,42 @@ TEST_F(LifetimeAnalysisTest, LivenessOutsideLoop) { EXPECT_THAT(Origins({"p"}), MaybeLiveAt("p1")); } +TEST_F(LifetimeAnalysisTest, TrivialDestructorsUAF) { + SetupTest(R"( + void target() { + int *ptr; + { + int s = 1; + ptr = &s; + } + POINT(p1); + (void)*ptr; + } + )"); + EXPECT_THAT(Origin("ptr"), HasLoansTo({"s"}, "p1")); + EXPECT_THAT(Origins({"ptr"}), MustBeLiveAt("p1")); +} + +TEST_F(LifetimeAnalysisTest, TrivialClassDestructorsUAF) { + SetupTest(R"( + class S { + View a, b; + }; + + void target() { + S* ptr; + { + S s; + ptr = &s; + } + POINT(p1); + (void)ptr; + } + )"); + EXPECT_THAT(Origin("ptr"), HasLoansTo({"s"}, "p1")); + EXPECT_THAT(Origins({"ptr"}), MustBeLiveAt("p1")); +} + TEST_F(LifetimeAnalysisTest, SimpleReturnStackAddress) { SetupTest(R"( MyObj* target() { @@ -1506,5 +1543,34 @@ TEST_F(LifetimeAnalysisTest, ReturnBeforeUseAfterScope) { EXPECT_THAT(Origins({"p"}), MustBeLiveAt("p1")); } +TEST_F(LifetimeAnalysisTest, TrivialDestructorsUAR) { + SetupTest(R"( + int* target() { + int s = 10; + int* p = &s; + POINT(p1); + return p; + } + )"); + EXPECT_THAT("s", HasLiveLoanAtExpiry("p1")); +} + +TEST_F(LifetimeAnalysisTest, TrivialClassDestructorsUAR) { + SetupTest(R"( + class S { + View a, b; + }; + + S* target() { + S *ptr; + S s; + ptr = &s; + POINT(p1); + return ptr; + } + )"); + EXPECT_THAT("s", HasLiveLoanAtExpiry("p1")); +} + } // anonymous namespace } // namespace clang::lifetimes::internal _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
