[asan] Rewrite Windows/heaprealloc_alloc_zero check to avoid dereference

[thurstond]

The test currently checks that 1-byte is allocated when malloc(0) is called, by dereferencing the pointer.
#155943 changed ASan to consider the dereference to be a heap buffer overflow. This patch changes the test to check the allocated size is still 1-byte, but not dereference the pointer.

This aims to fix the breakage reported in #155943 (comment)

It also enables the test for 64-bit Windows.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Thurston Dang (thurstond)

Changes

The test checks that 1-byte is allocated when malloc(0) is called, by dereferencing the pointer.
#155943 changed ASan to consider the dereference to be a heap buffer overflow. This patch changes the test to check the allocated size is still 1-byte, but not dereference the pointer.

This aims to fix the breakage reported in #155943 (comment)

---

Full diff: https://github.com/llvm/llvm-project/pull/156211.diff

1 Files Affected:

• (modified) compiler-rt/test/asan/TestCases/Windows/heaprealloc_alloc_zero.cpp (+7-1)

diff --git a/compiler-rt/test/asan/TestCases/Windows/heaprealloc_alloc_zero.cpp b/compiler-rt/test/asan/TestCases/Windows/heaprealloc_alloc_zero.cpp
index 8b0bc71b9f5db..e9be0d5b4c7df 100644
--- a/compiler-rt/test/asan/TestCases/Windows/heaprealloc_alloc_zero.cpp
+++ b/compiler-rt/test/asan/TestCases/Windows/heaprealloc_alloc_zero.cpp
@@ -3,13 +3,19 @@
 // UNSUPPORTED: asan-64-bits
 #include <cassert>
 #include <iostream>
+#include <sanitizer/allocator_interface.h>
 #include <windows.h>
 
 int main() {
   void *ptr = malloc(0);
   if (ptr)
     std::cerr << "allocated!\n";
-  ((char *)ptr)[0] = '\xff'; //check this 'allocate 1 instead of 0' hack hasn't changed
+
+  // Check the 'allocate 1 instead of 0' hack hasn't changed
+  // Note that as of b3452d90b043a398639e62b0ab01aa339cc649de, dereferencing
+  // the pointer will be detected as a heap-buffer-overflow.
+  if (__sanitizer_get_allocated_size(ptr) != 1)
+    return 1;
 
   free(ptr);
 

[mstorsjo]

LGTM, thanks! This does seem to fix the test for me.

(Side note - is the UNSUPPORTED: asan-64-bits still relevant here you think?)

[mstorsjo]

LGTM, thanks! This does seem to fix the test for me.

(Side note - is the UNSUPPORTED: asan-64-bits still relevant here you think?)

I checked; before b3452d9, this test did indeed fail on 64 bit. With the recent changes and this fix, this test does pass on 64 bit as well, so the UNSUPPORTED marking can be removed at the same time.

[thurstond]

LGTM, thanks! This does seem to fix the test for me.
(Side note - is the UNSUPPORTED: asan-64-bits still relevant here you think?)

I checked; before b3452d9, this test did indeed fail on 64 bit. With the recent changes and this fix, this test does pass on 64 bit as well, so the UNSUPPORTED marking can be removed at the same time.

Thanks for checking! I've Removed the UNSUPPORTED marking.