Hacker News Reader

Comment by PhilipRoman | Hacker News Reader

W^X is typically per mapping, not per memory page and does not interfere with JIT compilation.

Sure, but it still means that the OS has to decide who is allowed to do it and to what extent. Sophisticated worms like Stuxnet would be much harder with strict W^X for example, since CVE-2010-2568 and the like would be much harder to execute.

> Sure, but it still means that the OS has to decide who is allowed to do it and to what extent

It has to do that anyway?

Only if it wants to allow Writable Memory to become Executable, or basically, allow JIT.

How do you propose preventing that without a check?

Signed binaries with the proper assigned OS capabilities.

Yes, but with JIT, you can't really verify what the application does upfront. That is the entire point.

Capabilities are a way to control that, and the point being that only responsible proven applications get the certificate, hence how it all goes on iOS.

You're making the assumption that "responsible" is something provable, but that is not the case, it is specially not easy to prove software is secure from tampering its behaviour.

For that there is bytecode verification as intermediate step, and if you want to go crazy with security, hardware memory tagging with capabilities.

Which at this point most companies would rather save money and forbid JIT altogether.

Note that mainframes and micros have JIT environments that aren't at the same safety level as regular desktop PCs.

For example,

https://medium.com/@dhemanthc/ibm-i-architecture-how-timi-an...

Reply on news.ycombinator.com