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Don't validate signature for _VTblGap* methods #55616

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Jul 14, 2021
Merged

Don't validate signature for _VTblGap* methods #55616

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139 changes: 68 additions & 71 deletions src/coreclr/vm/methodtablebuilder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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)))
Expand All @@ -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;

{
Expand Down Expand Up @@ -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.
Expand Down