4 ms·

> The problem is right now DDR4 devices that work correctly in that regard, do not exist. Yes, and this is actually the problem. Without safe hardware, it is a

> The problem is right now DDR4 devices that work correctly in that regard, do not exist. Yes, and this is actually the problem. Without safe hardware, it is almost impossible to write safe software.

userbinator 5y ago
Meanwhile you can still buy DDR3 --- used --- from various shops in China, and it'll be 100% perfect and Rowhammer-free because it was made before the insane process shrinkages that caused it. (Have done this a few times. Was hesitant initially because of the low price and used nature, but when the first stick passed MemTest86+ including RH perfectly, I was convinced. Half a dozen more sticks later and still good. But maybe they've started to run out of the good old stuff now...)
- inetknght 5y ago
  > you can still buy DDR3 --- used --- from various shops in China, and it'll be 100% perfect and Rowhammer-free because it was made before the insane process shrinkages that caused it That's demonstrably false. I remember rowhammer being thought of and demonstrated on DDR3 modules. [0] https://hammertux.github.io/rowhammer-ffs-ddr3 https://hammertux.github.io/rowhammer-ffs-ddr3
  - userbinator 5y ago
    Rowhammer started appearing in newer DDR3; see the original paper (figure 3): https://news.ycombinator.com/item?id=8713411 https://news.ycombinator.com/item?id=8713411 The tl;dr is that everything 2009 and older is good, 2010-2011 is possibly bad, 2012 and newer is almost certainly bad.
throwaway81523 5y ago
> Yes, and this is actually the problem. Without safe hardware, it is almost impossible to write safe software. Software that attempts a hostile rowhammer attack aims to be unsafe by definition. It's not a matter of trying and failing to be safe. Rather, we're seeing that it's very difficult to build hardware and software that prevents hostile code from running amuck: if the attacker can run hostile code on your computer at all, you have already lost. That's bad news for cloud hosts and confirms what we already knew about web scripting, but doesn't seem all THAT bad for the rest of us. Of course it's possible to build computers with no DRAM at all (i.e. only SRAM, which costs more). That is not economically sane for big servers, but might be the right thing to do for security sensitive components.
- _0w8t 5y ago
  The sizes of current CPU caches is enough to run a lot of code…

> The problem is right now DDR4 devices that work correctly in that regard, do not exist. Yes, and this is actually the problem. Without safe hardware, it is almost impossible to write safe software.

userbinator 5y ago

Meanwhile you can still buy DDR3 --- used --- from various shops in China, and it'll be 100% perfect and Rowhammer-free because it was made before the insane process shrinkages that caused it. (Have done this a few times. Was hesitant initially because of the low price and used nature, but when the first stick passed MemTest86+ including RH perfectly, I was convinced. Half a dozen more sticks later and still good. But maybe they've started to run out of the good old stuff now...)

inetknght 5y ago
> you can still buy DDR3 --- used --- from various shops in China, and it'll be 100% perfect and Rowhammer-free because it was made before the insane process shrinkages that caused it That's demonstrably false. I remember rowhammer being thought of and demonstrated on DDR3 modules. [0] https://hammertux.github.io/rowhammer-ffs-ddr3 https://hammertux.github.io/rowhammer-ffs-ddr3
- userbinator 5y ago
  Rowhammer started appearing in newer DDR3; see the original paper (figure 3): https://news.ycombinator.com/item?id=8713411 https://news.ycombinator.com/item?id=8713411 The tl;dr is that everything 2009 and older is good, 2010-2011 is possibly bad, 2012 and newer is almost certainly bad.

throwaway81523 5y ago

> Yes, and this is actually the problem. Without safe hardware, it is almost impossible to write safe software. Software that attempts a hostile rowhammer attack aims to be unsafe by definition. It's not a matter of trying and failing to be safe. Rather, we're seeing that it's very difficult to build hardware and software that prevents hostile code from running amuck: if the attacker can run hostile code on your computer at all, you have already lost. That's bad news for cloud hosts and confirms what we already knew about web scripting, but doesn't seem all THAT bad for the rest of us. Of course it's possible to build computers with no DRAM at all (i.e. only SRAM, which costs more). That is not economically sane for big servers, but might be the right thing to do for security sensitive components.

_0w8t 5y ago
The sizes of current CPU caches is enough to run a lot of code…