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fix: validate tensor dims_count against the shared-memory region #438

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fix: validate tensor dims_count against the shared-memory region #438

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16 changes: 16 additions & 0 deletions src/pb_tensor.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -655,6 +655,22 @@ PbTensor::LoadFromSharedMemory(
AllocatedSharedMemory<char> tensor_shm = shm_pool->Load<char>(tensor_handle);
TensorShm* tensor_shm_ptr =
reinterpret_cast<TensorShm*>(tensor_shm.data_.get());

// Validate 'dims_count' against the shared-memory region before using it to
// compute offsets and read the dims array, to avoid an out-of-bounds read
// when the value is corrupted. The division avoids overflowing the
// 'sizeof(int64_t) * dims_count' product. Mirrors the MemoryShm::byte_size
// boundary check.
char* region_end = reinterpret_cast<char*>(shm_pool->GetBaseAddress()) +
shm_pool->GetCurrentCapacity();
char* dims_begin = tensor_shm.data_.get() + sizeof(TensorShm);
if (dims_begin > region_end ||
tensor_shm_ptr->dims_count >
static_cast<size_t>(region_end - dims_begin) / sizeof(int64_t)) {
throw PythonBackendException(
"Attempted to load a tensor with an out-of-bounds 'dims_count'");
}

size_t name_offset =
sizeof(TensorShm) + sizeof(int64_t) * tensor_shm_ptr->dims_count;
std::unique_ptr<PbString> name_shm = PbString::LoadFromSharedMemory(
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