5 ms·
This is misleading. I recommend [1] as an introduction to the semiconductor physics behind the Rowhammer problem. Rowhammer is an instance of the "weird machin
by xgk 3y ago
This is misleading.
I recommend [1] as an introduction to the semiconductor physics behind the Rowhammer problem. Rowhammer is an instance of the "weird machine" problem behind many security problems, i.e. a mismatch between two abstractions: the abstraction we pretend describes the system, vs the reality of the system. In the case of Rowhammer, that is the abstraction of memory as a digital device, against the reality of storing bits with capacitors and wires, ie. analog devices. Clearly a leaky abstraction. The denser you pack those capacitors and wires, the more leaky.
[1] A. J. Walker, S. Lee, D. Beery, On DRAM Rowhammer and the Physics of Insecurity. https://ieeexplore.ieee.org/document/9366976 https://ieeexplore.ieee.org/document/9366976
- theamk 3y agoI think it's important to differentiate "a mismatch between two abstractions" and "hardware bug". Because you can frame any sort of hardware (or even software!) problem like this: "Capacitor plague of 2000 was a mismatch between two abstractions: the abstraction that capacitor actually provides datasheet-described amount of capacitance vs the reality of the system" "Toyota unintended acceleration was a mismatch between two abstractions: the abstraction that ECU properly responds to accelerator pedal release vs the reality of the system" Yes, digital systems are made of analog parts, but that's not a reason to accept systems behaving out of spec. For the last 50 years, the specifications for RAM have been pretty clear: as long as all datasheet requirements are obeyed, the only way to change stored data in one location should be to do a write to that location. If a memory chip does not act according to its own datasheet, it's not a "leaky abstraction", it's a hardware bug. (Now, can this be fixed economically? I don't know, I could believe the answer is "no". However, the solution in this case is not software workarounds, but rather to make a new spec: "RH-RAM is like regular RAM but cannot tolerate certain access pattern")
- xgk 3y agoI think if you (row)hammer hard enough, every DRAM will eventually flip a bit.
- userbinator 3y agoRead the original Rowhammer paper where they tested various manufacturers and years --- this only started showing up around 2009, and DRAM from before that time was entirely immune to it.
- xgk 3y agoSorry, I should have said: ... (row)hammer hard enough, every sufficiently dense/modern DRAM ...