An Experimental Characterization of Combined RowHammer and RowPress Read Disturbance in Modern DRAM Chips

TL;DR

This paper experimentally characterizes the combined effects of RowHammer and RowPress disturbances in modern DDR4 DRAM chips, revealing faster bitflip induction and differing affected bits compared to individual patterns.

Contribution

It provides the first detailed analysis of combined RowHammer and RowPress effects across multiple DRAM manufacturers, highlighting their interaction and impact on memory reliability.

Findings

Combined pattern induces bitflips up to 46.1% faster.

Different bits flip under combined vs. individual patterns.

Read disturbance from RowPress is more significant from one aggressor row.

Abstract

DRAM read disturbance can break memory isolation, a fundamental property to ensure system robustness (i.e., reliability, security, safety). RowHammer and RowPress are two different DRAM read disturbance phenomena. RowHammer induces bitflips in physically adjacent victim DRAM rows by repeatedly opening and closing an aggressor DRAM row, while RowPress induces bitflips by keeping an aggressor DRAM row open for a long period of time. In this study, we characterize a DRAM access pattern that combines RowHammer and RowPress in 84 real DDR4 DRAM chips from all three major DRAM manufacturers. Our key results show that 1) this combined RowHammer and RowPress pattern takes significantly smaller amount of time (up to 46.1% faster) to induce the first bitflip compared to the state-of-the-art RowPress pattern, and 2) at the minimum aggressor row activation count to induce at least one bitflip, the bits that flip are different across RowHammer, RowPress, and the combined patterns. Based on our results, we provide a key hypothesis that the read disturbance effect caused by RowPress from one of the two aggressor rows in a double-sided pattern is much more significant than the other.