[compiler-rt] Fix possible underflow in ParseAndSetPath (PR #159389)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

Author: None (gbMattN)

<details>
<summary>Changes</summary>

If an empty path is passed, the internal_strlen -1 below will loop round to become uptr max. Adding this check ensures that this would be caught

---
Full diff: https://github.com/llvm/llvm-project/pull/159389.diff


1 Files Affected:

- (modified) compiler-rt/lib/sanitizer_common/sanitizer_file.cpp (+1) 


``````````diff
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp
index 9236a458cdb0e..49a44fa76fc9e 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp
@@ -106,6 +106,7 @@ static void ParseAndSetPath(const char *pattern, char *dest,
                             const uptr dest_size) {
   CHECK(pattern);
   CHECK(dest);
+  CHECK_NE(internal_strcmp(pattern, ""), 0);
   CHECK_GE(dest_size, 1);
   dest[0] = '\0';
   uptr next_substr_start_idx = 0;

``````````

</details>


https://github.com/llvm/llvm-project/pull/159389