A Rowhammer Reproduction Study Using the Blacksmith Fuzzer

Lukas Gerlach, Fabian Thomas, Robert Pietsch, Michael Schwarz

Rowhammer is a hardware vulnerability that can be exploited to induce bit flips in dynamic random access memory (DRAM), compromising the security of a computer system. Multiple ways of ex- ploiting Rowhammer have been shown and even in the presence of mitigations such as target row refresh (TRR), DRAM modules remain partially vulnerable. In this paper, we present a large-scale reproduction study on the Rowhammer vulnerability using the Blacksmith Rowhammer fuzzer. The main focus of our study is the impact of the fuzzing environment. Our study, uses a diverse set of 10 DRAM chips from various manufacturers, with different capacities and memory frequencies. We show that the runtime, used seeds, and DRAM coverage of the fuzzer have been underestimated in previous work. Additionally, we study the entire hard- ware setup’s impact on the transferability of Rowhammer by fuzzing the same DRAM on 4 identical machines. The transferability study heavily relates to Rowhammer-based physically unclonable functions (PUFs) which rely on the stability of Rowhammer-induced bit flips. Our results confirm the findings of the Blacksmith fuzzer, showing that even modern DRAM chips are vulnerable to Rowhammer. In addition, we show that PUFs are challenging to achieve on commodity systems due to the high variability of Rowhammer bit flips.