[llvm-branch-commits] [compiler-rt] release/19.x: [PAC][compiler-rt][UBSan] Strip signed vptr instead of authenticating it (#100153) (PR #100219)

[Tobias Hieta via llvm-branch-commits]

https://github.com/tru updated https://github.com/llvm/llvm-project/pull/100219

>From 95ed2d007951374c8ae905b2cce4be262865e442 Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanak at gmail.com>
Date: Tue, 23 Jul 2024 14:39:58 -0700
Subject: [PATCH] [PAC][compiler-rt][UBSan] Strip signed vptr instead of
 authenticating it (#100153)

vptr cannot be authenticated without knowing the class type if it was
signed with type discrimination.

Co-authored-by: Oliver Hunt <oliver at apple.com>
(cherry picked from commit 0a6a3c152faf56e07dd4f9e89e534d2b97eeab56)
---
 compiler-rt/lib/ubsan/ubsan_type_hash_itanium.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler-rt/lib/ubsan/ubsan_type_hash_itanium.cpp b/compiler-rt/lib/ubsan/ubsan_type_hash_itanium.cpp
index 468a8fcd603f0..15788574dd995 100644
--- a/compiler-rt/lib/ubsan/ubsan_type_hash_itanium.cpp
+++ b/compiler-rt/lib/ubsan/ubsan_type_hash_itanium.cpp
@@ -207,7 +207,7 @@ struct VtablePrefix {
   std::type_info *TypeInfo;
 };
 VtablePrefix *getVtablePrefix(void *Vtable) {
-  Vtable = ptrauth_auth_data(Vtable, ptrauth_key_cxx_vtable_pointer, 0);
+  Vtable = ptrauth_strip(Vtable, ptrauth_key_cxx_vtable_pointer);
   VtablePrefix *Vptr = reinterpret_cast<VtablePrefix*>(Vtable);
   VtablePrefix *Prefix = Vptr - 1;
   if (!IsAccessibleMemoryRange((uptr)Prefix, sizeof(VtablePrefix)))