7 ms·

> Many will cry about that performance hit (including me) because for over a decade our computers have gotten faster marginally, but our software has gotten slo

by boricj 4y ago

> Many will cry about that performance hit (including me) because for over a decade our computers have gotten faster marginally, but our software has gotten slower and bloatier at an increasingly rapid pace. We're talking about network stacks and network drivers, not web browsers. Migrating the network stack from the kernel to a user-land process is not going to measurably slow down web browsers, especially on modern systems with gigabytes of RAM, multiple cores, IOMMUs and whatnots. > These are memory bugs, so the introduction of Rust into the kernel could help us here potentially, no need for an architectural revolution. That would require rewriting the network stack and network drivers in Rust (driver code is much more likely to have bugs than the rest of the kernel) for this to be effective, otherwise you'll still have a lot of C code in the network path. I'd argue that this would be a bigger architectural revolution than porting the existing code and running it in user-land. MINIX3 went through such a change when drivers were removed from the kernel (can't find the publication about it right now) and they only required reasonably small changes when porting these to user-land, there were not rewritten from scratch. But this is not just about memory safety, Rust code can still be vulnerable in many other ways (memory leaks, unsafe blocks, wrong assumptions, incorrect algorithm implementation, buggy/compromised toolchains...). Code running inside the trusted computing base of a system is a liability, enforcing privilege separation and principle of least authority reduces it.

dijit 4y ago
> We're talking about network stacks and network drivers, not web browsers. Ah yes, the magic web-browser that doesn't do any kind of networking at all. > Migrating the network stack from the kernel to a user-land process is not going to measurably slow down web browsers, especially on modern systems with IOMMUs and whatnots. I don't know how you can possibly assert that, it's contradicting computer sciences' current understanding of operating system design as it relates to kernelmode/usermode switching, unless you're doing weird shared-memory things in userspace... which is terrifying. > That would require rewriting the network stack and network drivers in Rust Not really, C and Rust can interop just fine, you can have network drivers that are rust but the actual networking stack itself can remain C, if you want. > but this is not just about memory safety, Rust code can still be vulnerable in many other ways The post is literally memory safety bugs.
- detaro 4y ago
  > Ah yes, the magic web-browser that doesn't do any kind of networking at all. They clearly didn't claim that. Your webbrowser being slow nowadays is not because it needs to do some networking.
  - dijit 4y ago
    They are claiming a loss in performance is ok. I am claiming that people keep making this claim and it no longer holds true because software is already losing too much performance for the value we get back. That's my whole thesis.
    - jjnoakes 4y ago
      Your claim assumes that a small loss in performance in networking will lead to a loss in performance of the overall web browser, which is only true if networking is the bottleneck while browsing. And it usually isn't.
      - dijit 4y ago
        Ah, so you think the only thing I do with a computer is use the browser? That's weird, I was just making an example of something that is so slow that is literally unworkable in the modern day already. Impacting networking affects the entire machine, especially in so far as a computer is increasingly just a dumb terminal to something else. Look, If you make network requests potentially 20% slower then the browser performance will be impacted too, it's so obvious that I'm not sure how I can explain it simpler. By how much? I am not sure, but you can't say it won't be slower at all unless we're talking about magic. Pretending that it's trivial amounts of performance drop without evidence is the wrong approach. Show me how you can have similar performance with 20% increase in latency and I will change my stance here. As it stands there are two things I know to be true: Browsers rely on networking (as do many things, btw) and software is increasingly slow to provide similar value these days.
        4y ago
throw10920 4y ago
> I'd argue that this would be a bigger architectural revolution than porting the existing code and running it in user-land. MINIX3 went through such a change MINIX is a microkernel architecture - running drivers in userspace is one of its core features/selling points, and one that differentiates it from (modular) monolithic kernels such as Linux. So, this isn't a very solid line of reasoning. It seems to me that the situation is the opposite - that moving drivers to userspace is an architectural change, which is more complex than porting an existing architecture to a new language. > Rust code can still be vulnerable in many other ways Sure, but not vulnerable in the way that the vulnerability under discussion is. > memory leaks Much harder in Rust than C, and also unlike in C, not going to result in security vulnerabilities. > buggy/compromised toolchains If you're going to assume that your toolchain is compromised, than anything is on the table, including the toolchain inserting a backdoor into the kernel and completely bypassing the proposed architectural change of moving drivers into user-space. And, needless to say, compiler bugs are rare in general, and compiler bugs that cause software vulnerabilities are nearly unheard of (and I've literally never seen one before). Nobody thinking rationally is going to tell you that Rust is going to eliminate all your bugs or make your code secure. However, by far, the majority of security bugs in the Linux kernel are due to mistakes that the design of Rust either completely eliminates or massively reduces. And security is intrinsically a tradeoff - the Linux kernel is not optimized for maximum security (which would be something formally-verified like seL4), but a compromise between security, performance, and development velocity. The claim is that Rust will provide significantly better security at basically the same performance and possibly modestly improved development velocity - the very least that one should do is rewrite the existing architecture in it (or, again, a language that meets or exceeds the specs of Rust) and then see what the bug rate is before deciding to take a guaranteed performance hit through an architectural change.
- boricj 4y ago
  > MINIX is a microkernel architecture - running drivers in userspace is one of its core features/selling points, and one that differentiates it from (modular) monolithic kernels such as Linux. So, this isn't a very solid line of reasoning. The first two versions of MINIX ran drivers inside the context of the kernel. The migration of drivers to user-space and overall emphasis on reliability didn't happen before MINIX3 in 2006. Given that Linux nowadays has FUSE and UIO, still calling it a strictly monolithic kernel is probably a bit of a misnomer at this point. The same goes for Windows, NetBSD and others by the way. > It seems to me that the situation is the opposite - that moving drivers to userspace is an architectural change, which is more complex than porting an existing architecture to a new language. Trying to do a straightforward port of a C code base to Rust will quickly grind to a halt due to Rust's borrow checker. On a highly-optimized code base such as the Linux network stack, untangling every last optimization trick and shortcut to make the Rust compiler happy would require a large-scale refactoring that'll end up looking nothing like the original code base, at which point you might as well rewrite it from scratch. In comparison, migrating that C code base to user-land would be less of a disruptive change to the code base (as was the case when MINIX3 did so with its drivers). It's still the same old network stack, adapted to run on a different environment. > Sure, but not vulnerable in the way that the vulnerability under discussion is. Rust isn't a silver bullet against every class of bug. Code that runs inside the trusted computing base means that it's one security bug away from system compromise. Writing that code in Rust doesn't change that.

by boricj 4y ago

dijit 4y ago

> We're talking about network stacks and network drivers, not web browsers. Ah yes, the magic web-browser that doesn't do any kind of networking at all. > Migrating the network stack from the kernel to a user-land process is not going to measurably slow down web browsers, especially on modern systems with IOMMUs and whatnots. I don't know how you can possibly assert that, it's contradicting computer sciences' current understanding of operating system design as it relates to kernelmode/usermode switching, unless you're doing weird shared-memory things in userspace... which is terrifying. > That would require rewriting the network stack and network drivers in Rust Not really, C and Rust can interop just fine, you can have network drivers that are rust but the actual networking stack itself can remain C, if you want. > but this is not just about memory safety, Rust code can still be vulnerable in many other ways The post is literally memory safety bugs.

detaro 4y ago
> Ah yes, the magic web-browser that doesn't do any kind of networking at all. They clearly didn't claim that. Your webbrowser being slow nowadays is not because it needs to do some networking.
- dijit 4y ago
  They are claiming a loss in performance is ok. I am claiming that people keep making this claim and it no longer holds true because software is already losing too much performance for the value we get back. That's my whole thesis.
  - jjnoakes 4y ago
    Your claim assumes that a small loss in performance in networking will lead to a loss in performance of the overall web browser, which is only true if networking is the bottleneck while browsing. And it usually isn't.
    - dijit 4y ago
      Ah, so you think the only thing I do with a computer is use the browser? That's weird, I was just making an example of something that is so slow that is literally unworkable in the modern day already. Impacting networking affects the entire machine, especially in so far as a computer is increasingly just a dumb terminal to something else. Look, If you make network requests potentially 20% slower then the browser performance will be impacted too, it's so obvious that I'm not sure how I can explain it simpler. By how much? I am not sure, but you can't say it won't be slower at all unless we're talking about magic. Pretending that it's trivial amounts of performance drop without evidence is the wrong approach. Show me how you can have similar performance with 20% increase in latency and I will change my stance here. As it stands there are two things I know to be true: Browsers rely on networking (as do many things, btw) and software is increasingly slow to provide similar value these days.
      - 4y ago

throw10920 4y ago

> I'd argue that this would be a bigger architectural revolution than porting the existing code and running it in user-land. MINIX3 went through such a change MINIX is a microkernel architecture - running drivers in userspace is one of its core features/selling points, and one that differentiates it from (modular) monolithic kernels such as Linux. So, this isn't a very solid line of reasoning. It seems to me that the situation is the opposite - that moving drivers to userspace is an architectural change, which is more complex than porting an existing architecture to a new language. > Rust code can still be vulnerable in many other ways Sure, but not vulnerable in the way that the vulnerability under discussion is. > memory leaks Much harder in Rust than C, and also unlike in C, not going to result in security vulnerabilities. > buggy/compromised toolchains If you're going to assume that your toolchain is compromised, than anything is on the table, including the toolchain inserting a backdoor into the kernel and completely bypassing the proposed architectural change of moving drivers into user-space. And, needless to say, compiler bugs are rare in general, and compiler bugs that cause software vulnerabilities are nearly unheard of (and I've literally never seen one before). Nobody thinking rationally is going to tell you that Rust is going to eliminate all your bugs or make your code secure. However, by far, the majority of security bugs in the Linux kernel are due to mistakes that the design of Rust either completely eliminates or massively reduces. And security is intrinsically a tradeoff - the Linux kernel is not optimized for maximum security (which would be something formally-verified like seL4), but a compromise between security, performance, and development velocity. The claim is that Rust will provide significantly better security at basically the same performance and possibly modestly improved development velocity - the very least that one should do is rewrite the existing architecture in it (or, again, a language that meets or exceeds the specs of Rust) and then see what the bug rate is before deciding to take a guaranteed performance hit through an architectural change.

boricj 4y ago
> MINIX is a microkernel architecture - running drivers in userspace is one of its core features/selling points, and one that differentiates it from (modular) monolithic kernels such as Linux. So, this isn't a very solid line of reasoning. The first two versions of MINIX ran drivers inside the context of the kernel. The migration of drivers to user-space and overall emphasis on reliability didn't happen before MINIX3 in 2006. Given that Linux nowadays has FUSE and UIO, still calling it a strictly monolithic kernel is probably a bit of a misnomer at this point. The same goes for Windows, NetBSD and others by the way. > It seems to me that the situation is the opposite - that moving drivers to userspace is an architectural change, which is more complex than porting an existing architecture to a new language. Trying to do a straightforward port of a C code base to Rust will quickly grind to a halt due to Rust's borrow checker. On a highly-optimized code base such as the Linux network stack, untangling every last optimization trick and shortcut to make the Rust compiler happy would require a large-scale refactoring that'll end up looking nothing like the original code base, at which point you might as well rewrite it from scratch. In comparison, migrating that C code base to user-land would be less of a disruptive change to the code base (as was the case when MINIX3 did so with its drivers). It's still the same old network stack, adapted to run on a different environment. > Sure, but not vulnerable in the way that the vulnerability under discussion is. Rust isn't a silver bullet against every class of bug. Code that runs inside the trusted computing base means that it's one security bug away from system compromise. Writing that code in Rust doesn't change that.