[MSan] Fix check overflow in a test case

[Camsyn]

Supplement to PR #144073

Previously, msan_check_mem_is_initialized.cpp initialized a 32-byte stack array, but checked the shadow for the offset range [12, 42), exceeding the stack array size.

MSan does not guarantee that the shadow corresponding to the overflow part is 0, so it is undefined to require the overflow part to be unpoisoned.

[llvmbot]

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

Author: Kunqiu Chen (Camsyn)

Changes

Supplement to PR #144073

Previously, msan_check_mem_is_initialized.cpp initialized a 32-byte stack array, but checked the shadow for the offset range [12, 42), exceeding the stack array size.

MSan does not guarantee that the shadow corresponding to the overflow part is 0, so it is undefined to require the overflow part to be unpoisoned.

---

Full diff: https://github.com/llvm/llvm-project/pull/150429.diff

1 Files Affected:

• (modified) compiler-rt/test/msan/msan_check_mem_is_initialized.cpp (+1-1)

diff --git a/compiler-rt/test/msan/msan_check_mem_is_initialized.cpp b/compiler-rt/test/msan/msan_check_mem_is_initialized.cpp
index aaf5737ebe236..aab31893e01bc 100644
--- a/compiler-rt/test/msan/msan_check_mem_is_initialized.cpp
+++ b/compiler-rt/test/msan/msan_check_mem_is_initialized.cpp
@@ -12,7 +12,7 @@ int main(void) {
   __msan_poison(p + 10, 2);
 
   __msan_check_mem_is_initialized(p, 10);
-  __msan_check_mem_is_initialized(p + 12, 30);
+  __msan_check_mem_is_initialized(p + 12, 20);
 #ifdef POSITIVE
   __msan_check_mem_is_initialized(p + 5, 20);
   // CHECK: Uninitialized bytes in __msan_check_mem_is_initialized at offset 5 inside [0x{{.*}}, 20)

[fmayer]

LGTM thanks

Did this cause test failures for you?

[Camsyn]

Did this cause test failures for you?

I am implementing a sanitizer composition framework, which intends to support ASan, TSan and MSan.

This test failed in the scenario of -fsanitize=address,memory, where ASan modifies the size of this stack array.