Comment by rabite | Hacker News Reader

Comment by rabite | Hacker News Reader

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> Panics are safe though (they're a controlled crash).

Here's Linus's commentary on that:

https://lkml.org/lkml/2021/4/14/1099

> I think that if some Rust allocation can cause a panic, this is simply _fundamentally_ not acceptable.

> Allocation failures in a driver or non-core code - and that is by definition all of any new Rust code - can never EVER validly cause panics.

Panics are not acceptable in countless contexts. Plenty of things need to be written to keep working through entire categories of errors. The casual attitude of Rust developers towards error handling is one of the many reasons people have trouble taking it seriously. Reliability and robustness is generally more important than language memory safety for almost all contexts.

There are indeed many cases where errors need to be recovered from and the subject of one angle in secure rust code training was quite literally "don't just panic, don't blindly unwrap or leave errors unhandled because that'll kill your thread/process on failure, you should still code for failure cases". If you do, you are coding denial of service bugs.

But, in the incident in question, the code is fundamentally not correct. Spatial memory safety violations, or in plain English "trying to call functions or use data that isn't at addresses your code or data lives at" fundamentally is an error. There's a missing part of the state machine to detect and stop before just exploding. In userspace this is a segfault and your process dies. In kernel, you get a bugcheck and the whole system reboots.

There are scary alternatives. The first, in kernel, is that you suppress all invalid writes and allow the errant code to keep writing, until it hits some other data. The system stays up, but you have out of control data writes so who knows what that's doing.

The second is that the execution flow of the process can be hijacked, i.e. Sergey Bratus' weird machines, or in plainer language, owning kernels in critical infrastructure. This is usually undesirable.

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