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Fix write-heap-buffer-overflow in copy_out #15584

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Nov 11, 2025
+5 −3
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Fix write-heap-buffer-overflow in copy_out #15584

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8 changes: 5 additions & 3 deletions kernels/portable/cpu/op_copy.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,8 @@ Tensor& copy_out(
// Use direct copy fast path if broadcast is not needed and tensors are
// non-empty
if (internal::sizes_match_ignoring_leading_1s(out.sizes(), src.sizes()) &&
src.numel() > 0) {
src.numel() > 0 && out.nbytes() >= src.nbytes() &&
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@JacobSzwejbka JacobSzwejbka Nov 5, 2025

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@manuelcandales if numel are equal but nbytes isnt then should we be promoting the dtype here? Im not actually sure what copy_ does for mixed dtype?

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@lucylq lucylq Nov 5, 2025

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@JacobSzwejbka If nbytes isn't equal, it should go into the else statement, which I think handles different dtypes

tensors_have_same_dtype(src, out)) {
std::memcpy(out.mutable_data_ptr(), src.const_data_ptr(), src.nbytes());
} else {
ET_SWITCH_REALHBBF16_TYPES(in.scalar_type(), ctx, op_name, CTYPE, [&]() {
Expand Down Expand Up @@ -91,8 +92,9 @@ Tensor& copy_(
// Use direct copy fast path if broadcast is not needed and tensors are
// non-empty
if (internal::sizes_match_ignoring_leading_1s(in.sizes(), src.sizes()) &&
src.numel() > 0) {
std::memcpy(in.mutable_data_ptr(), src.const_data_ptr(), in.nbytes());
src.numel() > 0 && in.nbytes() >= src.nbytes() &&
tensors_have_same_dtype(src, in)) {
std::memcpy(in.mutable_data_ptr(), src.const_data_ptr(), src.nbytes());
} else {
ET_SWITCH_REALHBBF16_TYPES(in.scalar_type(), ctx, op_name, CTYPE, [&]() {
utils::apply_bitensor_elementwise_fn<
Expand Down
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