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Fix heap-buffer-overflow in constant_pad_nd with overflow-safe bounds checking #16468

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Merged
psiddh merged 1 commit into from
Jan 6, 2026
Merged

Fix heap-buffer-overflow in constant_pad_nd with overflow-safe bounds checking #16468

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30 changes: 20 additions & 10 deletions kernels/portable/cpu/op_constant_pad_nd.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@ void apply_padding_to_dim(
IntArrayRef self_sizes,
IntArrayRef self_strides,
CTYPE* out_data,
CTYPE* out_data_end,
IntArrayRef out_sizes,
IntArrayRef out_strides,
IntArrayRef pad,
Expand All @@ -59,14 +60,12 @@ void apply_padding_to_dim(
size_t in_step_len = self_strides[dim];

// Do not copy padding beyond the out tensor bounds.
// Use division to avoid potential overflow in multiplication.
if (pad_before > 0) {
size_t numel = 1;
for (ET_UNUSED const auto i : c10::irange(out_sizes.size())) {
numel *= out_sizes[i];
}
size_t remaining = out_data_end - out_data;
ET_KERNEL_CHECK_MSG(
ctx,
numel >= pad_before * out_step_len,
out_step_len > 0 && remaining / out_step_len >= pad_before,
InvalidArgument,
/* void */,
"Out tensor is too small for the requested padding.");
Expand All @@ -92,6 +91,15 @@ void apply_padding_to_dim(
InvalidArgument,
/* void */,
"Out tensor overlaps with the input tensor. This is not supported.");
// Bounds check before memcpy
// Use overflow-safe check for remaining >= copy_len
size_t remaining = out_data_end - out_data;
ET_KERNEL_CHECK_MSG(
ctx,
remaining >= copy_len,
InvalidArgument,
/* void */,
"Out tensor is too small for the copy operation.");
memcpy(out_data, self_data, copy_nbytes);
out_data += copy_len;
self_data += copy_len;
Expand All @@ -107,6 +115,7 @@ void apply_padding_to_dim(
self_sizes,
self_strides,
out_data,
out_data_end,
out_sizes,
out_strides,
pad,
Expand All @@ -120,14 +129,12 @@ void apply_padding_to_dim(
}

// Do not copy padding beyond the out tensor bounds.
// Use division to avoid potential overflow in multiplication.
if (pad_after > 0) {
size_t numel = 1;
for (ET_UNUSED const auto i : c10::irange(out_sizes.size())) {
numel *= out_sizes[i];
}
size_t remaining = out_data_end - out_data;
ET_KERNEL_CHECK_MSG(
ctx,
numel >= pad_after * out_step_len,
out_step_len > 0 && remaining / out_step_len >= pad_after,
InvalidArgument,
/* void */,
"Out tensor is too small for the requested padding.");
Expand Down Expand Up @@ -182,13 +189,16 @@ void constant_pad_nd_out_impl(
IntArrayRef out_sizes_ref(out_sizes, ndim);
IntArrayRef out_strides_ref(out_strides, ndim);

CTYPE* out_data_end = out_data + out.numel();

apply_padding_to_dim(
ctx,
ndim,
self_data,
self_sizes_ref,
self_strides_ref,
out_data,
out_data_end,
out_sizes_ref,
out_strides_ref,
pad,
Expand Down
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