[win/asan] Improve SharedReAlloc with HEAP_REALLOC_IN_PLACE_ONLY.

compiler-rt/lib/asan/asan_malloc_win.cpp

@@ -322,6 +322,22 @@ void *SharedReAlloc(ReAllocFunction reallocFunc, SizeFunction heapSizeFunc,
       }
     }
 
+    if (dwFlags & HEAP_REALLOC_IN_PLACE_ONLY) {
+      size_t old_usable_size = asan_malloc_usable_size(lpMem, pc, bp);
+      if (dwBytes == old_usable_size) {
+        // Nothing to change, return the current pointer.
+        return lpMem;
+      } else if (dwBytes >= old_usable_size) {
+        // Growing with HEAP_REALLOC_IN_PLACE_ONLY is not supported.
+        return nullptr;
+      } else {
+        // Shrinking with HEAP_REALLOC_IN_PLACE_ONLY is not yet supported.
+        // For now return the current pointer and
+        // leave the allocation size as it is.
+        return lpMem;
+      }
+    }
+
     if (ownershipState == ASAN && !only_asan_supported_flags) {
       // Conversion to unsupported flags allocation,
       // transfer this allocation back to the original allocator.

compiler-rt/test/asan/TestCases/Windows/rtlallocateheap_realloc_in_place.cpp

@@ -0,0 +1,71 @@
+// RUN: %clang_cl_asan %Od %s %Fe%t %MD
+// RUN: %env_asan_opts=windows_hook_rtl_allocators=true not %run %t 2>&1 | FileCheck %s
+
+#include <stdio.h>
+#include <windows.h>
+
+using AllocateFunctionPtr = PVOID(__stdcall *)(PVOID, ULONG, SIZE_T);
+using ReAllocateFunctionPtr = PVOID(__stdcall *)(PVOID, ULONG, PVOID, SIZE_T);
+using FreeFunctionPtr = PVOID(__stdcall *)(PVOID, ULONG, PVOID);
+
+int main() {
+  HMODULE NtDllHandle = GetModuleHandle("ntdll.dll");
+  if (!NtDllHandle) {
+    fputs("Couldn't load ntdll??\n", stderr);
+    return -1;
+  }
+
+  auto RtlAllocateHeap_ptr =
+      (AllocateFunctionPtr)GetProcAddress(NtDllHandle, "RtlAllocateHeap");
+  if (RtlAllocateHeap_ptr == 0) {
+    fputs("Couldn't RtlAllocateHeap\n", stderr);
+    return -1;
+  }
+
+  auto RtlReAllocateHeap_ptr =
+      (ReAllocateFunctionPtr)GetProcAddress(NtDllHandle, "RtlReAllocateHeap");
+  if (RtlReAllocateHeap_ptr == 0) {
+    fputs("Couldn't find RtlReAllocateHeap\n", stderr);
+    return -1;
+  }
+
+  auto RtlFreeHeap_ptr =
+      (FreeFunctionPtr)GetProcAddress(NtDllHandle, "RtlFreeHeap");
+  if (RtlFreeHeap_ptr == 0) {
+    fputs("Couldn't RtlFreeHeap\n", stderr);
+    return -1;
+  }
+
+  char *ptr1;
+  char *ptr2;
+  ptr2 = ptr1 = (char *)RtlAllocateHeap_ptr(GetProcessHeap(), 0, 15);
+  if (ptr1)
+    fputs("Okay alloc\n", stderr);
+  // CHECK: Okay alloc
+
+  // TODO: Growing is currently not supported
+  ptr2 = (char *)RtlReAllocateHeap_ptr(GetProcessHeap(),
+                                       HEAP_REALLOC_IN_PLACE_ONLY, ptr1, 23);
+  if (ptr2 == NULL)
+    fputs("Okay grow failed\n", stderr);
+  // CHECK: Okay grow failed
+
+  // TODO: Shrinking is currently not supported
+  ptr2 = (char *)RtlReAllocateHeap_ptr(GetProcessHeap(),
+                                       HEAP_REALLOC_IN_PLACE_ONLY, ptr1, 7);
+  if (ptr2 == ptr1)
+    fputs("Okay shrinking return the original pointer\n", stderr);
+  // CHECK: Okay shrinking return the original pointer
+
+  ptr1[7] = 'a';
+  fputs("Okay 7\n", stderr);
+  // CHECK: Okay 7
+
+  // TODO: Writing behind the shrinked part is currently not detected.
+  //       Therefore test writing behind the original allocation for now.
+  ptr1[16] = 'a';
+  // CHECK: AddressSanitizer: heap-buffer-overflow on address [[ADDR:0x[0-9a-f]+]]
+  // CHECK: WRITE of size 1 at [[ADDR]] thread T0
+
+  RtlFreeHeap_ptr(GetProcessHeap(), 0, ptr1);
+}