From 8d7afec55e93f011a3dc46c8e143dd56038bf197 Mon Sep 17 00:00:00 2001
From: Anna Zaks <ganna@apple.com>
Date: Tue, 27 Oct 2015 20:19:45 +0000
Subject: [PATCH] [analyzer] Assume escape is possible through system functions
taking void* The analyzer assumes that system functions will not free memory
or modify the arguments in other ways, so we assume that arguments do not
escape when those are called. However, this may lead to false positive leak
errors. For example, in code like this where the pointers added to the
rb_tree are freed later on:
struct alarm_event *e = calloc(1, sizeof(*e));
<snip>
rb_tree_insert_node(&alarm_tree, e);
Add a heuristic to assume that calls to system functions taking void*
arguments allow for pointer escape.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@251449 91177308-0d34-0410-b5e6-96231b3b80d8
---
.../Core/PathSensitive/CallEvent.h | 7 ++++
lib/StaticAnalyzer/Checkers/MallocChecker.cpp | 2 +-
lib/StaticAnalyzer/Core/CallEvent.cpp | 41 +++++++++++++------
.../Analysis/Inputs/system-header-simulator.h | 6 +++
test/Analysis/malloc.c | 17 ++++++++
5 files changed, 60 insertions(+), 13 deletions(-)
diff --git a/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h b/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
index cf888b5040e..77d73cfd1ee 100644
--- a/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
+++ b/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
@@ -254,9 +254,16 @@ public:
/// which the return value has already been bound to the origin expression.
SVal getReturnValue() const;
+ /// \brief Returns true if the type of any of the non-null arguments satisfies
+ /// the condition.
+ bool hasNonNullArgumentsWithType(bool (*Condition)(QualType)) const;
+
/// \brief Returns true if any of the arguments appear to represent callbacks.
bool hasNonZeroCallbackArg() const;
+ /// \brief Returns true if any of the arguments is void*.
+ bool hasVoidPointerToNonConstArg() const;
+
/// \brief Returns true if any of the arguments are known to escape to long-
/// term storage, even if this method will not modify them.
// NOTE: The exact semantics of this are still being defined!
diff --git a/lib/StaticAnalyzer/Checkers/MallocChecker.cpp b/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
index f924a767789..54b1a6ee0fd 100644
--- a/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
@@ -2390,7 +2390,7 @@ bool MallocChecker::mayFreeAnyEscapedMemoryOrIsModeledExplicitly(
if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(Call)) {
// If it's not a framework call, or if it takes a callback, assume it
// can free memory.
- if (!Call->isInSystemHeader() || Call->hasNonZeroCallbackArg())
+ if (!Call->isInSystemHeader() || Call->argumentsMayEscape())
return true;
// If it's a method we know about, handle it explicitly post-call.
diff --git a/lib/StaticAnalyzer/Core/CallEvent.cpp b/lib/StaticAnalyzer/Core/CallEvent.cpp
index f9d4ea22830..32c168819bf 100644
--- a/lib/StaticAnalyzer/Core/CallEvent.cpp
+++ b/lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -50,11 +50,7 @@ QualType CallEvent::getResultType() const {
return ResultTy;
}
-static bool isCallbackArg(SVal V, QualType T) {
- // If the parameter is 0, it's harmless.
- if (V.isZeroConstant())
- return false;
-
+static bool isCallback(QualType T) {
// If a parameter is a block or a callback, assume it can modify pointer.
if (T->isBlockPointerType() ||
T->isFunctionPointerType() ||
@@ -75,32 +71,53 @@ static bool isCallbackArg(SVal V, QualType T) {
return true;
}
}
-
return false;
}
-bool CallEvent::hasNonZeroCallbackArg() const {
+static bool isVoidPointerToNonConst(QualType T) {
+ if (const PointerType *PT = T->getAs<PointerType>()) {
+ QualType PointeeTy = PT->getPointeeType();
+ if (PointeeTy.isConstQualified())
+ return false;
+ return PointeeTy->isVoidType();
+ } else
+ return false;
+}
+
+bool CallEvent::hasNonNullArgumentsWithType(bool (*Condition)(QualType)) const {
unsigned NumOfArgs = getNumArgs();
// If calling using a function pointer, assume the function does not
- // have a callback. TODO: We could check the types of the arguments here.
+ // satisfy the callback.
+ // TODO: We could check the types of the arguments here.
if (!getDecl())
return false;
unsigned Idx = 0;
for (CallEvent::param_type_iterator I = param_type_begin(),
- E = param_type_end();
+ E = param_type_end();
I != E && Idx < NumOfArgs; ++I, ++Idx) {
if (NumOfArgs <= Idx)
break;
- if (isCallbackArg(getArgSVal(Idx), *I))
+ // If the parameter is 0, it's harmless.
+ if (getArgSVal(Idx).isZeroConstant())
+ continue;
+
+ if (Condition(*I))
return true;
}
-
return false;
}
+bool CallEvent::hasNonZeroCallbackArg() const {
+ return hasNonNullArgumentsWithType(isCallback);
+}
+
+bool CallEvent::hasVoidPointerToNonConstArg() const {
+ return hasNonNullArgumentsWithType(isVoidPointerToNonConst);
+}
+
bool CallEvent::isGlobalCFunction(StringRef FunctionName) const {
const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(getDecl());
if (!FD)
@@ -326,7 +343,7 @@ void AnyFunctionCall::getInitialStackFrameContents(
}
bool AnyFunctionCall::argumentsMayEscape() const {
- if (hasNonZeroCallbackArg())
+ if (CallEvent::argumentsMayEscape() || hasVoidPointerToNonConstArg())
return true;
const FunctionDecl *D = getDecl();
diff --git a/test/Analysis/Inputs/system-header-simulator.h b/test/Analysis/Inputs/system-header-simulator.h
index 8b8c9c4fe17..8605a2cbcb3 100644
--- a/test/Analysis/Inputs/system-header-simulator.h
+++ b/test/Analysis/Inputs/system-header-simulator.h
@@ -82,6 +82,12 @@ void xpc_connection_resume(xpc_connection_t connection);
void fakeSystemHeaderCallInt(int *);
void fakeSystemHeaderCallIntPtr(int **);
+// Some data strauctures may hold onto the pointer and free it later.
+void fake_insque(void *, void *);
+typedef struct fake_rb_tree { void *opaque[8]; } fake_rb_tree_t;
+void fake_rb_tree_init(fake_rb_tree_t *, const void *);
+void *fake_rb_tree_insert_node(fake_rb_tree_t *, void *);
+
typedef struct __SomeStruct {
char * p;
} SomeStruct;
diff --git a/test/Analysis/malloc.c b/test/Analysis/malloc.c
index 0962d0dbbfe..881eb38ad84 100644
--- a/test/Analysis/malloc.c
+++ b/test/Analysis/malloc.c
@@ -1657,6 +1657,23 @@ int *radar15580979() {
return p;
}
+// Some data structures may hold onto the pointer and free it later.
+void testEscapeThroughSystemCallTakingVoidPointer1(void *queue) {
+ int *data = (int *)malloc(32);
+ fake_insque(queue, data); // no warning
+}
+
+void testEscapeThroughSystemCallTakingVoidPointer2(fake_rb_tree_t *rbt) {
+ int *data = (int *)malloc(32);
+ fake_rb_tree_init(rbt, data);
+} //expected-warning{{Potential leak}}
+
+void testEscapeThroughSystemCallTakingVoidPointer3(fake_rb_tree_t *rbt) {
+ int *data = (int *)malloc(32);
+ fake_rb_tree_init(rbt, data);
+ fake_rb_tree_insert_node(rbt, data); // no warning
+}
+
// ----------------------------------------------------------------------------
// False negatives.
--
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