Reland "[libclang] Always Dup in createRef(StringRef)"

[vitalybuka]

Reverts #127076 to reland #125020

Use-after-free should be fixed here #127063

[llvmbot]

@llvm/pr-subscribers-clang

Author: Vitaly Buka (vitalybuka)

Changes

Reverts llvm/llvm-project#127076

---

Full diff: https://github.com/llvm/llvm-project/pull/127078.diff

2 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+3)
• (modified) clang/tools/libclang/CXString.cpp (+1-13)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 03bddbe3e983a..e41ad384b84f7 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -257,6 +257,9 @@ clang-format
 libclang
 --------
 
+- Fixed a buffer overflow in ``CXString`` implementation. The fix may result in
+  increased memory allocation.
+
 Code Completion
 ---------------
 
diff --git a/clang/tools/libclang/CXString.cpp b/clang/tools/libclang/CXString.cpp
index 5e427957a1092..aaa8f8eeb67a1 100644
--- a/clang/tools/libclang/CXString.cpp
+++ b/clang/tools/libclang/CXString.cpp
@@ -87,19 +87,7 @@ CXString createRef(StringRef String) {
   if (String.empty())
     return createEmpty();
 
-  // If the string is not nul-terminated, we have to make a copy.
-
-  // FIXME: This is doing a one past end read, and should be removed! For memory
-  // we don't manage, the API string can become unterminated at any time outside
-  // our control.
-
-  if (String.data()[String.size()] != 0)
-    return createDup(String);
-
-  CXString Result;
-  Result.data = String.data();
-  Result.private_flags = (unsigned) CXS_Unmanaged;
-  return Result;
+  return createDup(String);
 }
 
 CXString createDup(StringRef String) {

[vitalybuka]

It passes now https://lab.llvm.org/buildbot/#/builders/24/builds/5488

[vitalybuka]

@fmayer Looks like my patch exposed another UAF
https://lab.llvm.org/buildbot/#/builders/169/builds/8637

Looking, and will revert if there is no quick fix