Hacker News Reader

Comment by carlmr | Hacker News Reader

How is JIT miscompilation or vulnerabilities in the JIT compiler not an issue?

A Ruby program can delete all of the files on a computer, insert arbitrary rows into a database, drop a table, send email with attachments, etc. Am I correct that you're concerned the Ruby JIT itself will have a security vulnerability in the act of JIT compiling Ruby code? This seems extremely myopic.

JS engines have had many serious vulnerabilities in their JIT optimizers, it’s not myopic at all and is a well known technique in the industry.

I agree that some folks aren’t executing untrusted ruby code so they wouldn’t have to worry about this - but how many PaaS/SaaS products out there are? Or how about third party dev tools that are blindly downloaded and executed on local workstations or CI pipelines?

> JS engines have had many serious vulnerabilities in their JIT optimizers, it’s not myopic at all and is a well known technique in the industry.

HotSpot and V8 are both written in C++ and get more use than any other JIT on Earth.

Can you provide a link to a CVE caused by JIT miscompilation and explain how Rust would have been able to prevent the bug in a way that C++ wouldn't?

> I agree that some folks aren’t executing untrusted ruby code so they wouldn’t have to worry about this - but how many PaaS/SaaS products out there are?

This is what Xen, KVM, and Hyper-V do.

> Or how about third party dev tools that are blindly downloaded and executed on local workstations or CI pipelines?

Are you suggesting a Ruby JIT shouldn't generate machine code that corresponds to the Ruby program, but somehow magically prevent stupid developers from doing stupid things?

It's a bad look if a malicious HTTP request to your Rails app can trigger RCE on your server. It's not about running code that's malicious, it's about bad data triggering a code path in the VM that is able to change the function of the application.

What you're describing is a logic bug.

JITs write instructions to memory in a manner that's only slightly different than writing bytes to a file. The generation of those instructions can either be correct or incorrect and happens regardless of programming language.

A JIT written in Python is equally capable of generating bad code as a JIT written in C or Rust or Lisp. A perfect port of a buggy JIT written in language A will generate the same buggy code even after being ported to language B.

Reply on news.ycombinator.com