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Integer overflow in PlatformMemoryAllocator::allocate() #18680

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Integer overflow in PlatformMemoryAllocator::allocate() #18680

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16 changes: 14 additions & 2 deletions runtime/executor/platform_memory_allocator.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
#include <cinttypes>
#include <cstdint>

#include <c10/util/safe_numerics.h>
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Copilot AI Apr 2, 2026

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<c10/util/safe_numerics.h> is already included by executorch/runtime/core/memory_allocator.h, so this direct include is redundant here. Consider removing it to keep header dependencies minimal and reduce rebuild churn.

Suggested change
#include <c10/util/safe_numerics.h>

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#include <executorch/runtime/core/memory_allocator.h>
#include <executorch/runtime/platform/log.h>
#include <executorch/runtime/platform/platform.h>
Expand Down Expand Up @@ -46,8 +47,19 @@ class PlatformMemoryAllocator final : public MemoryAllocator {
return nullptr;
}

// Allocate enough memory for the node, the data and the alignment bump.
size_t alloc_size = sizeof(AllocationNode) + size + alignment;
// Check for overflow before computing total allocation size.
// Then allocate enough memory for node, data and the alignment bump.
size_t alloc_size = 0;
if (c10::add_overflows(sizeof(AllocationNode), size, &alloc_size) ||
c10::add_overflows(alloc_size, alignment, &alloc_size)) {
Comment on lines +51 to +54
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Copilot AI Apr 2, 2026

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The allocation “alignment bump” only needs to reserve up to alignment - 1 bytes. Using + alignment slightly over-allocates and can also make the overflow check reject an allocation that would otherwise fit by 1 byte. Consider adding alignment - 1 (after validating alignment > 0, which isPowerOf2 already implies) instead of alignment.

Suggested change
// Then allocate enough memory for node, data and the alignment bump.
size_t alloc_size = 0;
if (c10::add_overflows(sizeof(AllocationNode), size, &alloc_size) ||
c10::add_overflows(alloc_size, alignment, &alloc_size)) {
// Then allocate enough memory for node, data and the maximum alignment
// bump, which is at most alignment - 1 bytes.
size_t alloc_size = 0;
if (c10::add_overflows(sizeof(AllocationNode), size, &alloc_size) ||
c10::add_overflows(alloc_size, alignment - 1, &alloc_size)) {

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ET_LOG(
Error,
"Allocation size overflow: size %zu, alignment %zu",
size,
alignment);
return nullptr;
}

void* node_memory = runtime::pal_allocate(alloc_size);

// If allocation failed, log message and return nullptr.
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