poc-pytorch-symint-overflow

PoC: SymInt computeStorageNbytesContiguous Integer Overflow

Vulnerability

The SymInt version of computeStorageNbytesContiguous at aten/src/ATen/EmptyTensor.cpp:132-139 performs arithmetic on c10::SymInt values without ANY overflow checking, on ALL platforms. The regular (IntArrayRef) version uses safe_multiplies_u64/add_overflows/mul_overflows on desktop builds, but the SymInt version has no such protection.

When SymInt wraps concrete int64_t values, SymInt::operator* (c10/core/SymInt.h:195) performs plain *ma * *mb — signed int64_t multiplication with no overflow check.

Files

• poc_symint_overflow.py — Full PoC with 5 tests demonstrating the overflow
• symint_overflow_ext.cpp — C++ extension that directly exercises the vulnerable code paths

Quick Reproduction

pip install torch
git clone https://huggingface.co/0xiviel/poc-pytorch-symint-overflow
cd poc-pytorch-symint-overflow
python poc_symint_overflow.py

Requirements

• PyTorch (tested on 2.10.0+cpu)
• C++ compiler (g++ or clang++)
• ninja (pip install ninja)

Impact

• Heap OOB read: 16,380 bytes of heap data leaked via undersized tensor
• Heap OOB write: Process crashes with SIGSEGV (heap corruption)
• Affects ALL platforms (not just mobile)