https://github.com/necto created
https://github.com/llvm/llvm-project/pull/107003
Assigning to a pointer parameter does not leak the stack address because it
stays within the function and is not shared with the caller.
Previous implementation reported any association of a pointer parameter with a
local address, which is too broad.
This fix enforces that the pointer to a stack variable is related by at least
one level of indirection.
CPP-5642
Fixes #106834
>From da5671efccd0ba56a0dd983b04d1f798c5c35d0d Mon Sep 17 00:00:00 2001
From: Arseniy Zaostrovnykh <necto...@gmail.com>
Date: Mon, 2 Sep 2024 17:13:14 +0200
Subject: [PATCH] [analyzer] Fix false positive for stack-addr leak on simple
param ptr
Assigning to a pointer parameter does not leak the stack address because
it stays within the function and is not shared with the caller.
Previous implementation reported any association of a pointer parameter
with a local address, which is too broad.
This fix enforces that the pointer to a stack variable is related by at
least one level of indirection.
CPP-5642
Fixes #106834
---
.../Checkers/StackAddrEscapeChecker.cpp | 2 ++
clang/test/Analysis/stack-addr-ps.cpp | 27 +++++++++++++++++++
2 files changed, 29 insertions(+)
diff --git a/clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
b/clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
index ec577c36188e6c..5394c2257514dc 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
@@ -420,6 +420,8 @@ void StackAddrEscapeChecker::checkEndFunction(const
ReturnStmt *RS,
return true;
}
if (isa<StackArgumentsSpaceRegion>(ReferrerMemSpace) &&
+ // Not a simple ptr (int*) but something deeper, e.g. int**
+ isa<SymbolicRegion>(Referrer->getBaseRegion()) &&
ReferrerStackSpace->getStackFrame() == PoppedFrame && TopFrame) {
// Output parameter of a top-level function
V.emplace_back(Referrer, Referred);
diff --git a/clang/test/Analysis/stack-addr-ps.cpp
b/clang/test/Analysis/stack-addr-ps.cpp
index 88bf6512165201..3c922dfb0ed454 100644
--- a/clang/test/Analysis/stack-addr-ps.cpp
+++ b/clang/test/Analysis/stack-addr-ps.cpp
@@ -791,3 +791,30 @@ void global_ptr_to_ptr() {
*global_pp = nullptr;
}
} // namespace leaking_via_indirect_global_invalidated
+
+namespace not_leaking_via_simple_ptr {
+void top(const char *p) {
+ char tmp;
+ p = &tmp;
+}
+
+extern void copy(char *output, const char *input, unsigned size);
+extern bool foo(const char *input);
+extern void bar(char *output, unsigned count);
+extern bool baz(char *output, const char *input);
+
+void repo(const char *input, char *output) {
+ char temp[64];
+ copy(temp, input, sizeof(temp));
+
+ char result[64];
+ input = temp;
+ if (foo(temp)) {
+ bar(result, sizeof(result));
+ input = result;
+ }
+ if (!baz(output, input)) {
+ copy(output, input, sizeof(result));
+ }
+}
+} // namespace not_leaking_via_simple_ptr
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