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[UBSAN] add null and alignment checks for aggregates #164548

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[UBSAN] add null and alignment checks for aggregates #164548

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856ac3b
add null and aligment checks for aggregates
Oct 22, 2025
a42a794
Merge branch 'main' into vasu/add-null-and-alignment-checks-for-aggre…
vasu-the-sharma Oct 22, 2025
4b7ff1e
Add null and alignment checks for aggregate copy operation
Oct 22, 2025
85ee368
Merge branch 'main' into vasu/add-null-and-alignment-checks-for-aggre…
vasu-the-sharma Oct 22, 2025
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15 changes: 15 additions & 0 deletions clang/lib/CodeGen/CGExprAgg.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2249,6 +2249,21 @@ void CodeGenFunction::EmitAggregateCopy(LValue Dest, LValue Src, QualType Ty,
bool isVolatile) {
assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");

if (SanOpts.hasOneOf(SanitizerKind::Null | SanitizerKind::Alignment)) {
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I recommend omitting this check and leaving sanitizePerformTypeCheck to do its work.

Address SrcAddr = Src.getAddress();
Address DestAddr = Dest.getAddress();

// Check source pointer for null and alignment violations
EmitTypeCheck(TCK_Load, SourceLocation(),
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I think the scope should be expanded to other cases covered by EmitCheckedLValue.

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@vasu-the-sharma vasu-the-sharma Oct 28, 2025 •
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Thanks for the suggestion @hubert-reinterpretcast
I've reviewed the two EmitCheckedLValue usage sites in CGExprAgg.cpp:

Line 802 (VisitCastExpr): Uses EmitCheckedLValue with TCK_Load for dynamic_cast operations
Line 1313 (VisitBinAssign): Uses EmitCheckedLValue with TCK_Store, then calls EmitCopy which delegates to EmitAggregateCopy

Both cases are already covered:
EmitCheckedLValue performs type checking on the LValue expression itself
My changes to EmitAggregateCopy add sanitizer checks at the actual copy operation (the memcpy call)

These checks are complementary rather than redundant:
EmitCheckedLValue: Validates the expression evaluation produces a valid LValue
EmitAggregateCopy: Validates the source and destination pointers during the memory copy operation

The EmitAggregateCopy checks catch cases where pointers might become invalid between LValue emission and the actual copy (like array indexing or pointer arithmetic).
Do you see other specific cases in EmitCheckedLValue usage that would benefit from additional instrumentation?

SrcAddr.emitRawPointer(*this), Ty, SrcAddr.getAlignment(),
SanitizerSet());

// Check destination pointer for null and alignment violations
EmitTypeCheck(TCK_Store, SourceLocation(),
DestAddr.emitRawPointer(*this), Ty, DestAddr.getAlignment(),
SanitizerSet());
}

Address DestPtr = Dest.getAddress();
Address SrcPtr = Src.getAddress();

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