Don't validate signature for _VTblGap* methods (#55616)

diff --git a/src/coreclr/vm/methodtablebuilder.cpp b/src/coreclr/vm/methodtablebuilder.cpp
index 154c642..b426204 100644 (file)
--- a/src/coreclr/vm/methodtablebuilder.cpp
+++ b/src/coreclr/vm/methodtablebuilder.cpp
@@ -2751,15 +2751,7 @@ MethodTableBuilder::EnumerateClassMethods()
             BuildMethodTableThrowException(IDS_CLASSLOAD_BADFORMAT);
         }
 
-        // Signature validation
-        if (!bmtProp->fNoSanityChecks)
-        {
-            hr = validateTokenSig(tok,pMemberSignature,cMemberSignature,dwMemberAttrs,pMDInternalImport);
-            if (FAILED(hr))
-            {
-                BuildMethodTableThrowException(hr, BFA_BAD_SIGNATURE, mdMethodDefNil);
-            }
-        }
+        bool isVtblGap = false;
         if (IsMdRTSpecialName(dwMemberAttrs) || IsMdVirtual(dwMemberAttrs) || IsDelegate())
         {
             if (FAILED(pMDInternalImport->GetNameOfMethodDef(tok, (LPCSTR *)&strMethodName)))
@@ -2770,12 +2762,24 @@ MethodTableBuilder::EnumerateClassMethods()
             {
                 BuildMethodTableThrowException(BFA_METHOD_NAME_TOO_LONG);
             }
+
+            isVtblGap = IsMdRTSpecialName(dwMemberAttrs) && strncmp(strMethodName, "_VtblGap", 8) == 0;
         }
         else
         {
             strMethodName = NULL;
         }
 
+        // Signature validation
+        if (!bmtProp->fNoSanityChecks && !isVtblGap)
+        {
+            hr = validateTokenSig(tok,pMemberSignature,cMemberSignature,dwMemberAttrs,pMDInternalImport);
+            if (FAILED(hr))
+            {
+                BuildMethodTableThrowException(hr, BFA_BAD_SIGNATURE, mdMethodDefNil);
+            }
+        }
+
         DWORD numGenericMethodArgs = 0;
 
         {
@@ -2847,85 +2851,78 @@ MethodTableBuilder::EnumerateClassMethods()
         // single empty slot).
         //
 
-        if (IsMdRTSpecialName(dwMemberAttrs))
+        if (isVtblGap)
         {
-            PREFIX_ASSUME(strMethodName != NULL); // if we've gotten here we've called GetNameOfMethodDef
-
-            // The slot is special, but it might not be a vtable spacer. To
-            // determine that we must look at the name.
-            if (strncmp(strMethodName, "_VtblGap", 8) == 0)
-            {
-                                //
-                // This slot doesn't really exist, don't add it to the method
-                // table. Instead it represents one or more empty slots, encoded
-                // in the method name. Locate the beginning of the count in the
-                // name. There are these points to consider:
-                //   There may be no count present at all (in which case the
-                //   count is taken as one).
-                //   There may be an additional count just after Gap but before
-                //   the '_'. We ignore this.
-                                //
+            //
+            // This slot doesn't really exist, don't add it to the method
+            // table. Instead it represents one or more empty slots, encoded
+            // in the method name. Locate the beginning of the count in the
+            // name. There are these points to consider:
+            //   There may be no count present at all (in which case the
+            //   count is taken as one).
+            //   There may be an additional count just after Gap but before
+            //   the '_'. We ignore this.
+            //
 
-                LPCSTR pos = strMethodName + 8;
+            LPCSTR pos = strMethodName + 8;
 
-                // Skip optional number.
-                while (IS_DIGIT(*pos))
-                    pos++;
+            // Skip optional number.
+            while (IS_DIGIT(*pos))
+                pos++;
 
-                WORD n = 0;
+            WORD n = 0;
 
-                // Check for presence of count.
-                if (*pos == '\0')
-                    n = 1;
-                else
+            // Check for presence of count.
+            if (*pos == '\0')
+            {
+                n = 1;
+            }
+            else
+            {
+                if (*pos != '_')
                 {
-                    if (*pos != '_')
-                    {
-                        BuildMethodTableThrowException(COR_E_BADIMAGEFORMAT,
-                                                       IDS_CLASSLOAD_BADSPECIALMETHOD,
-                                                       tok);
-                    }
+                    BuildMethodTableThrowException(COR_E_BADIMAGEFORMAT,
+                                                    IDS_CLASSLOAD_BADSPECIALMETHOD,
+                                                    tok);
+                }
 
-                    // Skip '_'.
-                    pos++;
+                // Skip '_'.
+                pos++;
 
-                    // Read count.
-                    bool fReadAtLeastOneDigit = false;
-                    while (IS_DIGIT(*pos))
-                    {
-                        _ASSERTE(n < 6552);
-                        n *= 10;
-                        n += DIGIT_TO_INT(*pos);
-                        pos++;
-                        fReadAtLeastOneDigit = true;
-                    }
+                // Read count.
+                bool fReadAtLeastOneDigit = false;
+                while (IS_DIGIT(*pos))
+                {
+                    _ASSERTE(n < 6552);
+                    n *= 10;
+                    n += DIGIT_TO_INT(*pos);
+                    pos++;
+                    fReadAtLeastOneDigit = true;
+                }
 
-                    // Check for end of name.
-                    if (*pos != '\0' || !fReadAtLeastOneDigit)
-                    {
-                        BuildMethodTableThrowException(COR_E_BADIMAGEFORMAT,
-                                                       IDS_CLASSLOAD_BADSPECIALMETHOD,
-                                                       tok);
-                    }
+                // Check for end of name.
+                if (*pos != '\0' || !fReadAtLeastOneDigit)
+                {
+                    BuildMethodTableThrowException(COR_E_BADIMAGEFORMAT,
+                                                    IDS_CLASSLOAD_BADSPECIALMETHOD,
+                                                    tok);
                 }
+            }
 
 #ifdef FEATURE_COMINTEROP
-                // Record vtable gap in mapping list. The map is an optional field, so ensure we've allocated
-                // these fields first.
-                EnsureOptionalFieldsAreAllocated(GetHalfBakedClass(), m_pAllocMemTracker, GetLoaderAllocator()->GetLowFrequencyHeap());
-                if (GetHalfBakedClass()->GetSparseCOMInteropVTableMap() == NULL)
-                    GetHalfBakedClass()->SetSparseCOMInteropVTableMap(new SparseVTableMap());
+            // Record vtable gap in mapping list. The map is an optional field, so ensure we've allocated
+            // these fields first.
+            EnsureOptionalFieldsAreAllocated(GetHalfBakedClass(), m_pAllocMemTracker, GetLoaderAllocator()->GetLowFrequencyHeap());
+            if (GetHalfBakedClass()->GetSparseCOMInteropVTableMap() == NULL)
+                GetHalfBakedClass()->SetSparseCOMInteropVTableMap(new SparseVTableMap());
 
-                GetHalfBakedClass()->GetSparseCOMInteropVTableMap()->RecordGap((WORD)NumDeclaredMethods(), n);
+            GetHalfBakedClass()->GetSparseCOMInteropVTableMap()->RecordGap((WORD)NumDeclaredMethods(), n);
 
-                bmtProp->fSparse = true;
+            bmtProp->fSparse = true;
 #endif // FEATURE_COMINTEROP
-                continue;
-            }
-
+            continue;
         }
 
-
         //
         // This is a real method so add it to the enumeration of methods. We now need to retrieve
         // information on the method and store it for later use.