[compiler-rt] [HWASan] Prevent same tag for adjacent heap objects (PR #69337)

[via llvm-commits]

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@@ -0,0 +1,41 @@
+// Test that adjacent heap objects are always tagged differently to prevent unexpected under- and overflows.
+// RUN: %clang_hwasan %s -o %t
+// RUN: %env_hwasan_opts=random_tags=1,disable_allocator_tagging=0 %run %t
+
+#include <assert.h>
+#include <sanitizer/allocator_interface.h>
+#include <sanitizer/hwasan_interface.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static const size_t sizes[] = {16, 32, 64, 128, 256, 512, 1024, 2048};
+
+void check_collisions_on_heap(size_t size) {
+  // Allocate 3 heap objects, which should be placed next to each other
+  void *a = malloc(size);
+  void *b = malloc(size);
+  void *c = malloc(size);
+
+  // Confirm that no object can access adjacent objects
+  assert(__hwasan_test_shadow(a, size + 1) != -1);
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KonradHohentanner wrote:

I modified the check to compare the return value with the size, and added checks to ensure the left side is inaccessible.

https://github.com/llvm/llvm-project/pull/69337