Comment by lmm
2 years ago
> It requires deep understanding of the code (i.e. what it does, why it is doing it that way and the implied effect of executing the code on the architecture) and also of the architecture (i.e. how it is executing and why that causes leakage to be observable via the side-channel).
For exploitation, or for patching, maybe. But characterizing these bugs is still clear and simple IMO. I mean, rowhammer is about as basic as a bug can get - the value of this bit in memory changed even though it was never written to.
Rowhammer isn't a speculative execution bug. Without getting into how complex Rowhammer is or isn't, speculative execution is an inherently complex and software-involved pattern of vulnerability.
You're letting yourself get dragged into some weird rhetorical places trying to defend this part of Raymond's essay.
> Rowhammer isn't a speculative execution bug. Without getting into how complex Rowhammer is or isn't, speculative execution is an inherently complex and software-involved pattern of vulnerability.
Rowhammer was one of the examples the person I was replying to listed. But the same applies for spectre/meltdown/etc.. They're all issues that can be understood - perhaps not exploited, certainly not fixed, but understood that a bug is there - without any deep architectural knowledge.
> You're letting yourself get dragged into some weird rhetorical places trying to defend this part of Raymond's essay.
If anyone other than you talked like this they'd be quite rightly downvoted to oblivion.
> They're all issues that can be understood - perhaps not exploited, certainly not fixed, but understood that a bug is there - without any deep architectural knowledge.
I don't think it is clear how you would do this other than with hindsight. When the bug was discovered, if we avoid architectural knowledge of why the bug was occurring then what information would the discoverer have access to?
- Memory corruption is occuring during execution.
- We can't find any part of code that appears to corrupt the values.
Finding the bug requires finding the Rowhammer affect, which means looking isolating the instructions that are accessing similar uncached addresses, and then finding the pattern of accesses and cache flushes which triggers the corruption.
Could you explain how this would be simple, or do you have a different view of the bug complexity that you could explain?
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Yes, they provided several examples, and then you attempted to tie them all together and claim they were conceptually simple. No, that won't fly.