[compiler-rt] [ASan] Change strdup interceptor to allow null input on Windows (PR #122803)

[Zack Johnson via llvm-commits]

https://github.com/zacklj89 updated https://github.com/llvm/llvm-project/pull/122803

>From dd3b042e065450f1cfd79910c3705dce6e1d0810 Mon Sep 17 00:00:00 2001
From: Zack Johnson <zacklj89 at gmail.com>
Date: Mon, 13 Jan 2025 13:57:19 -0500
Subject: [PATCH 1/4] Change strdup interceptor to allow null input on Windows

---
 compiler-rt/lib/asan/asan_interceptors.cpp       |  6 ++++++
 .../TestCases/Windows/msvc/strdup_null_input.cpp | 16 ++++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 compiler-rt/test/asan/TestCases/Windows/msvc/strdup_null_input.cpp

diff --git a/compiler-rt/lib/asan/asan_interceptors.cpp b/compiler-rt/lib/asan/asan_interceptors.cpp
index e6c95dfb82c320..a2dc2bbf54bdb1 100644
--- a/compiler-rt/lib/asan/asan_interceptors.cpp
+++ b/compiler-rt/lib/asan/asan_interceptors.cpp
@@ -584,6 +584,12 @@ INTERCEPTOR(char *, strcpy, char *to, const char *from) {
 INTERCEPTOR(char*, strdup, const char *s) {
   void *ctx;
   ASAN_INTERCEPTOR_ENTER(ctx, strdup);
+#if SANITIZER_WINDOWS
+  // Allowing null input is Windows-specific
+  if (UNLIKELY(!s)) {
+    return nullptr;
+  }
+#endif
   if (UNLIKELY(!TryAsanInitFromRtl()))
     return internal_strdup(s);
   uptr length = internal_strlen(s);
diff --git a/compiler-rt/test/asan/TestCases/Windows/msvc/strdup_null_input.cpp b/compiler-rt/test/asan/TestCases/Windows/msvc/strdup_null_input.cpp
new file mode 100644
index 00000000000000..d84b2f501927ce
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/Windows/msvc/strdup_null_input.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cl_asan %s -Fe%t.exe
+// RUN: %run %t.exe | FileCheck %s
+
+// CHECK: Success
+
+#include <malloc.h>
+#include <stdio.h>
+#include <string.h>
+
+int main() {
+  // Null input is valid to strdup on Windows.
+  char *nullStr = _strdup(nullptr);
+  free(nullStr);
+  puts("Success");
+  return 0;
+}
\ No newline at end of file

>From 087256742f64ad21bd3a4ffdbee03c2be1d44461 Mon Sep 17 00:00:00 2001
From: Zack Johnson <zacklj89 at gmail.com>
Date: Mon, 13 Jan 2025 17:07:55 -0500
Subject: [PATCH 2/4] Formatting fix

---
 compiler-rt/lib/asan/asan_interceptors.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler-rt/lib/asan/asan_interceptors.cpp b/compiler-rt/lib/asan/asan_interceptors.cpp
index a2dc2bbf54bdb1..8411b1e17f211c 100644
--- a/compiler-rt/lib/asan/asan_interceptors.cpp
+++ b/compiler-rt/lib/asan/asan_interceptors.cpp
@@ -584,12 +584,12 @@ INTERCEPTOR(char *, strcpy, char *to, const char *from) {
 INTERCEPTOR(char*, strdup, const char *s) {
   void *ctx;
   ASAN_INTERCEPTOR_ENTER(ctx, strdup);
-#if SANITIZER_WINDOWS
+#  if SANITIZER_WINDOWS
   // Allowing null input is Windows-specific
   if (UNLIKELY(!s)) {
     return nullptr;
   }
-#endif
+#  endif
   if (UNLIKELY(!TryAsanInitFromRtl()))
     return internal_strdup(s);
   uptr length = internal_strlen(s);

>From 132b53e92583d66eb7901c048cf9e4486883d78d Mon Sep 17 00:00:00 2001
From: Zack Johnson <zacklj89 at gmail.com>
Date: Mon, 13 Jan 2025 19:52:40 -0500
Subject: [PATCH 3/4] Single line conditional and remove braces

---
 compiler-rt/lib/asan/asan_interceptors.cpp | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/compiler-rt/lib/asan/asan_interceptors.cpp b/compiler-rt/lib/asan/asan_interceptors.cpp
index 8411b1e17f211c..247ea1b92f1f42 100644
--- a/compiler-rt/lib/asan/asan_interceptors.cpp
+++ b/compiler-rt/lib/asan/asan_interceptors.cpp
@@ -584,12 +584,9 @@ INTERCEPTOR(char *, strcpy, char *to, const char *from) {
 INTERCEPTOR(char*, strdup, const char *s) {
   void *ctx;
   ASAN_INTERCEPTOR_ENTER(ctx, strdup);
-#  if SANITIZER_WINDOWS
   // Allowing null input is Windows-specific
-  if (UNLIKELY(!s)) {
+  if (SANITIZER_WINDOWS && UNLIKELY(!s))
     return nullptr;
-  }
-#  endif
   if (UNLIKELY(!TryAsanInitFromRtl()))
     return internal_strdup(s);
   uptr length = internal_strlen(s);

>From 68cab2d51bd77a8e82f45415c3634723fc3218eb Mon Sep 17 00:00:00 2001
From: Zack Johnson <zacklj89 at gmail.com>
Date: Tue, 14 Jan 2025 11:48:34 -0500
Subject: [PATCH 4/4] Updating test file end

---
 .../test/asan/TestCases/Windows/msvc/strdup_null_input.cpp      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler-rt/test/asan/TestCases/Windows/msvc/strdup_null_input.cpp b/compiler-rt/test/asan/TestCases/Windows/msvc/strdup_null_input.cpp
index d84b2f501927ce..9fd34fe9a08dd1 100644
--- a/compiler-rt/test/asan/TestCases/Windows/msvc/strdup_null_input.cpp
+++ b/compiler-rt/test/asan/TestCases/Windows/msvc/strdup_null_input.cpp
@@ -13,4 +13,4 @@ int main() {
   free(nullStr);
   puts("Success");
   return 0;
-}
\ No newline at end of file
+}