amazing, that’s a long chain of things that needed to happen for it to fail... also, never assume any kind of sizes!
New blog post: Debugging an evil Go runtime bughttps://marcan.st/2017/12/debugging-an-evil-go-runtime-bug/ …
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That's how real hackers debug binaries. I've followed the situation on Twitter and I thought it was bad RAM too!
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I wonder if rr would have helped here?
@rocallahan@khuey_ -
If it doesn't make assumptions about stack layout or use of libc, then quite likely. I was going to mention reverse execution debugging as a powerful approach that might've worked but I wasn't sure of any examples.
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What a nasty bug... I'm amazed you're able to track down all of that.
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I have a bit of a history of debugging horribly nasty stuff. Stories at Google I can't really detail include out-of-bounds read in a zlib implementation breaking once-in-a-petabyte and a kernel panic causing cross-pollination of data between files that broke a downstream process.
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It took about 3 days of, I guess, probably full-time equivalent work.
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This is a neat read. I’ll have to read the last third of it again, though; I’m not much of a developer and not that familiar with the system internals and got lost partway through.
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If there are any particular bits that could use some extra explanation I'll be happy to amend it :)
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It doesn't matter that "or" isn't atomic or not a no-op. It's supposed to be probing unused stack space.
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