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Retr0idyesterday at 9:43 PM2 repliesview on HN

Intel MEE addressed this (https://eprint.iacr.org/2016/204.pdf), by treating DRAM as entirely untrusted (assuming an attacker with arbitrary physical read/write capabilities), but then they discontinued it.

Regarding your linked comment:

> If we had properly tested and validated RAM, RowHammer wouldn't work, ever.

While it's exacerbated by physical defects and tight timings, it's really a fundamental problem with how DRAM works. It's frankly a miracle it works in the first place.


Replies

inigyouyesterday at 10:02 PM

No. If it was designed really well, it would trigger extra refreshes as needed. It would know how much accessing a row disturbs nearby rows and how much disturbance a row can suffer before it needs a refresh to prevent data corruption. It would know how long a row can be held open for, too. There is no fundamental theorem that rowhammer must work. It was an engineering tradeoff.

I don't think we can blame DRAM designers for flying a teensy bit too close to the sun here, since this is no problem in normal operation and only appears under adversarial scenarios. We can blame them for not fixing it once it was discovered. And we can definitely blame Intel for making ECC RAM a market segmentation feature.

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anon_rh_guytoday at 12:00 AM

Little known fun fact: the MEE's checksum updates... were one of the most successful Rowhammer patterns... :-p

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