[cfi] Safe handling of unaddressable vtable pointers (compiler-rt).

Avoid crashing when printing diagnostics for vtable-related CFI
errors. In diagnostic mode, the frontend does an additional check of
the vtable pointer against the set of all known vtable addresses and
lets the runtime handler know if it is safe to inspect the vtable.

http://reviews.llvm.org/D16824

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@259717 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 5 deletions

diff --git a/lib/ubsan/ubsan_handlers_cxx.cc b/lib/ubsan/ubsan_handlers_cxx.cc
index 739b4ca4a..593b15e12 100644
--- a/lib/ubsan/ubsan_handlers_cxx.cc
+++ b/lib/ubsan/ubsan_handlers_cxx.cc
@@ -90,7 +90,7 @@ void __ubsan::__ubsan_handle_dynamic_type_cache_miss_abort(
 
 namespace __ubsan {
 void HandleCFIBadType(CFICheckFailData *Data, ValueHandle Vtable,
-                      ReportOptions Opts) {
+                      bool ValidVtable, ReportOptions Opts) {
   SourceLocation Loc = Data->Loc.acquire();
   ErrorType ET = ErrorType::CFIBadType;
 
@@ -98,7 +98,9 @@ void HandleCFIBadType(CFICheckFailData *Data, ValueHandle Vtable,
     return;
 
   ScopedReport R(Opts, Loc, ET);
-  DynamicTypeInfo DTI = getDynamicTypeInfoFromVtable((void *)Vtable);
+  DynamicTypeInfo DTI = ValidVtable
+                            ? getDynamicTypeInfoFromVtable((void *)Vtable)
+                            : DynamicTypeInfo(0, 0, 0);
 
   const char *CheckKindStr;
   switch (Data->CheckKind) {
@@ -123,11 +125,16 @@ void HandleCFIBadType(CFICheckFailData *Data, ValueHandle Vtable,
       << Data->Type << CheckKindStr << (void *)Vtable;
 
   // If possible, say what type it actually points to.
-  if (!DTI.isValid())
-    Diag(Vtable, DL_Note, "invalid vtable");
-  else
+  if (!DTI.isValid()) {
+    const char *module = Symbolizer::GetOrInit()->GetModuleNameForPc(Vtable);
+    if (module)
+      Diag(Vtable, DL_Note, "invalid vtable in module %0") << module;
+    else
+      Diag(Vtable, DL_Note, "invalid vtable");
+  } else {
     Diag(Vtable, DL_Note, "vtable is of type %0")
         << TypeName(DTI.getMostDerivedTypeName());
+  }
 }
 }  // namespace __ubsan