unbounded heap growth crashes xst, xsnap (SIGSEGV)

[dckc]

Steps to Reproduce

1. xst grow.js where grow.js is given below
   • whether release or debug build
2. SIGSEGV

let stuff = '1234';
for (;;) {
  stuff += stuff;
}

It also crashes xsnap, debug and release.

Build environment: Linux
Target device: xst

cc @warner

somewhat related: Agoric/agoric-sdk#2276 , Agoric/agoric-sdk#2224

[phoddie]

Hmmm... yes, that happens. I know it used to work correctly. Interesting, the embedded targets seem fine. On an ESP32 for example, there's no crash: it lands in fxAbort with an error value of XS_NOT_ENOUGH_MEMORY_EXIT. So, strictly speaking, this looks like a bug in port to certain targets rather than a bug in XS itself.

[dckc]

yay! seems to be fixed in c22a50b.

[phoddie]

It turns out to be a more complex issue than it first appeared. On systems with limited memory, it isn't a practical concern. On systems with lots of memory (gigabytes) it can be.

We put in a workaround for the problem you reported. It isn't a proper fix for all situations. We should come back to this at some point.

[dckc]

yeah... I saw txSize is 4 bytes... I can see how that could run into overflow.

I do prefer to track this until a proper fix is available. Memory safety is job 1!

[dckc]

I'm not sure what to verify; the symptoms I was seeing were fixed Feb 22 by c22a50b.

I don't have any way to provoke the more general problem handy.

[phoddie]

As the problems you could reproduce are resolved, this can be closed.