  DRAM cells are susceptible to Data-Disturbance Errors (DDE), which can be
exploited by an attacker to compromise system security. Rowhammer is a
well-known DDE vulnerability that occurs when a row is repeatedly activated.
Rowhammer can be mitigated by tracking aggressor rows inside DRAM (in-DRAM) or
at the Memory Controller (MC). Row-Press (RP) is a new DDE vulnerability that
occurs when a row is kept open for a long time. RP significantly reduces the
number of activations required to induce an error, thus breaking existing RH
solutions. Prior work on Explicit Row-Press mitigation, ExPress, requires the
memory controller to limit the maximum row-open-time, and redesign existing
Rowhammer solutions with reduced Rowhammer threshold. Unfortunately, ExPress
incurs significant performance and storage overheads, and being a memory
controller-based solution, it is incompatible with in-DRAM trackers. In this
paper, we propose Implicit Row-Press mitigation (ImPress), which does not
restrict row-open-time, is compatible with memory controller-based and in-DRAM
solutions and does not reduce the tolerated Rowhammer threshold. ImPress treats
a row open for a specified time as equivalent to an activation. We design
ImPress by developing a Unified Charge-Loss Model, which combines the net
effect of both Rowhammer and Row-Press for arbitrary patterns. We analyze both
controller-based (Graphene and PARA) and in-DRAM trackers (Mithril and MINT).
We show that ImPress makes Rowhammer solutions resilient to Row-Press
transparently, without affecting the Rowhammer threshold.
