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Comment by pcwalton | Hacker News Reader

So, if that's true, why is Chrome considered to have solved Spectre? Browser content processes from different domains share some memory. Moreover, if process boundaries don't have any effect on the branch predictor on current hardware, then why is process separation relevant at all? Doesn't all this mean Spectre is still an issue?

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I guess I jumped the gun a bit in my comment above.

In terms of the possibility of exploit, as I understand there isn't at this point any isolation between processes.

In terms of the ease of exploit, being able to run untrusted code in the same process as the victim helps quite a bit. Otherwise, you have to find a gadget (i.e. qualifying bounds check for v1, indirect branch for v2) in the victim process that you can exploit from the attacker process. Possible, but quite a bit harder than making your own gadget.

This all ignores the forward looking reasons process isolation is a good idea. I can't keep track of the latest mitigations in Linux, but they pretty much all will only help between processes by flushing various hardware data structures. And hopefully someday we will have hardware actually designed to restore the guarantees of isolation between processes.

I'm pretty sure this is accurate, but I'm just a random guy on the internet so don't trust my word for it too much.

It's not really about process isolation then, but the amount of control untrusted code can have over a process. Which means if everything that code can do is masked to some part of the process, it should be able to achieve the same isolation between such subprocesses but within the OS process boundaries. Although the paper claims this is too hard.

Chromium does not fully solved Spectre. It is still too expensive to run one process per domain, so many unrelated pages run in the same process. But Chromium contains a few mitigations that makes exploiting Spectre from JS much harder.

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