Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Try to make sudo less vulnerable to Rowhammer attacks

github.com

Post reply on HN
Print view View original

131–140 of 147 posts

Re: Try to make sudo less vulnerable to Rowhammer attacks

#131

Post by theamk »

bogantech wrote: post #119
userbinator wrote: post #112

No. Do not want. Rowhammer is a hardware problem ---- defective RAM --- not a software one. The sooner everyone starts returning defective RAM and putting pressure on the hardware manufacturers to maintain correctness, the sooner we can stop this descent into insanity. "They can always work around it in software" is the attitude that let Rowhammer exist, and continuing to fulfill that expectation will only make thing…

> Rowhammer is a hardware problem ---- defective RAM --- not a software one. It always amazes me how people can be so confident yet so wrong. It's a problem of physics - there's various ways to try to mitigate it but the only way to completely avoid it would probably be to use SRAM and that is going to be extremely expensive when talking 16GB and not nearly dense enough. It's not some conspiracy by "Big RAM"

There are plenty of problems of physics in the RAM design, and it's hardware designers jobs to find the operating regime where those problems do not matter.

I mean, if you had a DRAM labeled "DDR4-3200" but it can only work at a much lower speed (say DDR4-2400), it's clearly a problem of physics - the gate capacitance is too high, the driver transistors are not strong enough. And yet my reaction would be to take that RAM back to store and get my money back, not to defend manufacturers which claim false things about their chips.

Re: Try to make sudo less vulnerable to Rowhammer attacks

#132

Post by randomdata »

IshKebab wrote: post #121
randomdata wrote: post #51

Earlier quoted context omitted.

Yet the vocal majority of Rust users present themselves as being inexperienced programmers. I expect it is not just an act – that the vocal majority truly are inexperienced, and I expect the segment of users who are novices is much larger than you suggest. The fact of the matter is that the novices have always been drawn to the 'hot new technology' and it is unlikely that Rust, being today's 'hot new technology', is…

> the vocal majority of Rust users present themselves as being inexperienced programmers No they don't.

They do. To be fair, vocal majorities generally are inexperienced, even outside of Rust communities. Of course they are. What would someone with experience gain from such vocal exchange?

The vocal majority of Rust users are especially vocal in tech circles right now, though, because of it being the "hot new technology" and thus most attractive to inexperienced programmers. This does make their inexperience stand out in an especially prominent way. All "hot new technologies" have gone through this pain period.

That doesn't mean that there aren't experienced Rust users, but experienced users have no reason to talk about it. Their experience has already collected everything that could be gained through vocalization. Talking about it becomes boring at that point.

Re: Try to make sudo less vulnerable to Rowhammer attacks

#133

Post by rurban »

wongarsu wrote: post #79
nuccy wrote: post #58

Earlier quoted context omitted.

Not really. An example out of top of my head, where this still might be useful are login nodes (used in many research clusters to allow users to enter and sumbit jobs) or shared web-hosting servers (few of those definitely still exist). There legitimate non-privileged users can run their programs and the end goal is to prevent them from getting root.

The last time I looked at the statistics the majority of the internet was still running on PHP, mostly wordpress installs. I'm willing to bet those are mostly on shared hosting with accounts separated by nothing but their linux user.

Last time I looked, 70% of the internet runs on cPanel, which uses my perl compiler.

Re: Try to make sudo less vulnerable to Rowhammer attacks

#134

Post by xgk »

theamk wrote: post #130
xgk wrote: post #127

Earlier quoted context omitted.

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 reali…

I 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 betwe…

I think if you (row)hammer hard enough, every DRAM will eventually flip a bit.

Re: Try to make sudo less vulnerable to Rowhammer attacks

#135

Post by rstuart4133 »

bogantech wrote: post #119
userbinator wrote: post #112

No. Do not want. Rowhammer is a hardware problem ---- defective RAM --- not a software one. The sooner everyone starts returning defective RAM and putting pressure on the hardware manufacturers to maintain correctness, the sooner we can stop this descent into insanity. "They can always work around it in software" is the attitude that let Rowhammer exist, and continuing to fulfill that expectation will only make thing…

> Rowhammer is a hardware problem ---- defective RAM --- not a software one. It always amazes me how people can be so confident yet so wrong. It's a problem of physics - there's various ways to try to mitigate it but the only way to completely avoid it would probably be to use SRAM and that is going to be extremely expensive when talking 16GB and not nearly dense enough. It's not some conspiracy by "Big RAM"

> It's a problem of physics - there's various ways to try to mitigate it but the only way to completely avoid it would probably be to use SRAM and that is going to be extremely expensive when talking 16GB and not nearly dense enough.

And yet, when the bit flip problem caused by physics got so bad in DDR5 it couldn't be ignored they did fix it - by adding error correction codes. It wasn't that expensive to do so. Notice that HDD's hit the same problem as the got denser, and solved it in the same way (ie, by throwing lots of ECC at it).

I agree with the original poster. It's a hardware problem, caused by the manufacturers pushing the limits. And it's their problem to fix, which they can do. DRAM that doesn't corrupt itself isn't a big ask.

Re: Try to make sudo less vulnerable to Rowhammer attacks

#136

Post by userbinator »

xgk wrote: post #134
theamk wrote: post #130

Earlier quoted context omitted.

I 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 betwe…

I think if you (row)hammer hard enough, every DRAM will eventually flip a bit.

Read 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.

Re: Try to make sudo less vulnerable to Rowhammer attacks

#137

Post by userbinator »

bogantech wrote: post #119
userbinator wrote: post #112

No. Do not want. Rowhammer is a hardware problem ---- defective RAM --- not a software one. The sooner everyone starts returning defective RAM and putting pressure on the hardware manufacturers to maintain correctness, the sooner we can stop this descent into insanity. "They can always work around it in software" is the attitude that let Rowhammer exist, and continuing to fulfill that expectation will only make thing…

> Rowhammer is a hardware problem ---- defective RAM --- not a software one. It always amazes me how people can be so confident yet so wrong. It's a problem of physics - there's various ways to try to mitigate it but the only way to completely avoid it would probably be to use SRAM and that is going to be extremely expensive when talking 16GB and not nearly dense enough. It's not some conspiracy by "Big RAM"

"It always amazes me how people can be so confident yet so wrong" could apply to your post too.

Yes it's a problem of physics and it's because they are trying to make DRAM too dense.

It's a problem of physics - there's various ways to try to mitigate it but the only way to completely avoid it would probably be to use SRAM

It's not some conspiracy by "Big RAM"

Look at the evidence. This didn't start showing up until around 2009-2010, and the industry managed to convince authors of widely-used memory testing tools to downplay the severity and/or not enable RH tests by default, because they didn't want the truth to be known that almost all RAM is defective. It might not be a conspiracy, but it sure is corporate greed.

Would you rather pay a little more for RAM that will work correctly under all access patterns, or RAM that is certain to produce bit errors under some conditions that can be encountered in practice? Unfortunately, with newer DDR3 and later generations, it seems you don't get a choice.

Re: Try to make sudo less vulnerable to Rowhammer attacks

#138

Post by kevincox »

Beldin wrote: post #116
deadliftdouche wrote: post #110

Earlier quoted context omitted.

I'd argue its worse than pointless, at best it does nothing and at worse it seems to make the code harder to understand and audit, which could result in more future vulnerabilities.

The associated paper abstract claims to have broken sudo by rowhammering register values. It stands to reason that these mitigations thwart the found attacks - the commit message points to the paper as the reason for these mitigations, after all. Preventing known attacks is not pointless at all.

I think the point is that if your known attack I'd "target was shot in the right hand" making them wear a protective glove on their right hand isn't a good defense. You would want two protective gloves, a helmet and bulletproof vest.

Re: Try to make sudo less vulnerable to Rowhammer attacks

#139

Post by kevincox »

kzrdude wrote: post #56

When do these values get into memory, shouldn't they be in registers generally? Maybe it's when the program loaded to memory to execute, but is that part rowhammerable?

If a task is preempted it will have its registers saved to memory. So you can never assume that some state won't live in memory at some point.

Re: Try to make sudo less vulnerable to Rowhammer attacks

#140

Post by DANmode »

userbinator wrote: post #137
bogantech wrote: post #119

Earlier quoted context omitted.

> Rowhammer is a hardware problem ---- defective RAM --- not a software one. It always amazes me how people can be so confident yet so wrong. It's a problem of physics - there's various ways to try to mitigate it but the only way to completely avoid it would probably be to use SRAM and that is going to be extremely expensive when talking 16GB and not nearly dense enough. It's not some conspiracy by "Big RAM"

"It always amazes me how people can be so confident yet so wrong" could apply to your post too. Yes it's a problem of physics and it's because they are trying to make DRAM too dense. It's a problem of physics - there's various ways to try to mitigate it but the only way to completely avoid it would probably be to use SRAM It's not some conspiracy by "Big RAM" Look at the evidence. This didn't start showing up until a…

You get a "choice".

The choice just boils down to "buy pricey server boards/chipsets that have ECC RAM available" or "get bent".

Post reply on HN