[compiler-rt] adaf5ba - Fix possible underflow in ParseAndSetPath (#159389)

[via llvm-commits]

Author: gbMattN
Date: 2025-09-18T16:11:46+01:00
New Revision: adaf5ba6791e7b32dd6dca2f857d588a5304d7e7

URL: https://github.com/llvm/llvm-project/commit/adaf5ba6791e7b32dd6dca2f857d588a5304d7e7
DIFF: https://github.com/llvm/llvm-project/commit/adaf5ba6791e7b32dd6dca2f857d588a5304d7e7.diff

LOG: Fix possible underflow in ParseAndSetPath (#159389)

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

Added: 
    

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_file.cpp

Removed: 
    


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diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp
index 9236a458cdb0e..a2c0a9c39d04e 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp
@@ -108,6 +108,9 @@ static void ParseAndSetPath(const char *pattern, char *dest,
   CHECK(dest);
   CHECK_GE(dest_size, 1);
   dest[0] = '\0';
+  // Return empty string if empty string was passed
+  if (internal_strlen(pattern) == 0)
+    return;
   uptr next_substr_start_idx = 0;
   for (uptr i = 0; i < internal_strlen(pattern) - 1; i++) {
     if (pattern[i] != '%')