[libc-commits] [libc] 0239ada - [libc] Mark return value of memcpy in strcpy as initialized for msan.

[Siva Chandra Reddy via libc-commits]

Author: Siva Chandra Reddy
Date: 2021-09-01T19:01:25Z
New Revision: 0239adac4aa09900937d08ababf34e43bfca1442

URL: https://github.com/llvm/llvm-project/commit/0239adac4aa09900937d08ababf34e43bfca1442
DIFF: https://github.com/llvm/llvm-project/commit/0239adac4aa09900937d08ababf34e43bfca1442.diff

LOG: [libc] Mark return value of memcpy in strcpy as initialized for msan.

Reviewed By: michaelrj

Differential Revision: https://reviews.llvm.org/D109045

Added: 
    

Modified: 
    libc/src/string/strcpy.cpp

Removed: 
    


################################################################################
diff  --git a/libc/src/string/strcpy.cpp b/libc/src/string/strcpy.cpp
index d081d6c497df..d5b72d9d92f6 100644
--- a/libc/src/string/strcpy.cpp
+++ b/libc/src/string/strcpy.cpp
@@ -11,13 +11,25 @@
 #include "src/string/string_utils.h"
 
 #include "src/__support/common.h"
+#include "src/__support/sanitizer.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(char *, strcpy,
                    (char *__restrict dest, const char *__restrict src)) {
-  return reinterpret_cast<char *>(
-      __llvm_libc::memcpy(dest, src, internal::string_length(src) + 1));
+  size_t size = internal::string_length(src) + 1;
+  char *result = reinterpret_cast<char *>(__llvm_libc::memcpy(dest, src, size));
+
+  // In many libc uses, we do not want memcpy to be instrumented. Hence,
+  // we mark the destination as initialized.
+  //
+  // We do not want memcpy to be instrumented because compilers can potentially
+  // generate calls to memcpy. If the sanitizer business logic ends up with a
+  // compiler generated call to memcpy which is instrumented, then it will
+  // break the sanitizers.
+  SANITIZER_MEMORY_INITIALIZED(result, size);
+
+  return result;
 }
 
 } // namespace __llvm_libc