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Very cool. I'd guess you still want to reboot every once in a while to clean up memory, but since you won't have any security updates pending you can schedule t

by mmelin 17y ago

Very cool. I'd guess you still want to reboot every once in a while to clean up memory, but since you won't have any security updates pending you can schedule the reboot at your leisure. The pessimist in me says to wait until a botched patch causes systems worldwide to crash and burn, though. It would also be interesting to find out more about Ksplice's own security as they are now in a position to create the mother of all DoS attacks.

pbhjpbhj 17y ago
>wait until a botched patch causes systems worldwide to crash and burn I'm not following you here. Why does reboot-less updating of the kernel mean that the patches won't be tested. Also what DoS attack were you thinking of? Lastly, clean up memory? The top uptimes on Netcraft are >1000 days, is this necessary, are there specific memory leaks you're considering?
- mmelin 17y ago
  Using Ksplice means that you're letting a private company inject custom code directly into your running kernel. The paper explains that most Linux security updates are applied without modification, but some updates require Ksplice to write custom code for the patches to work (specifically if the update changes any data structures). My pessimistic side says that sooner or later this custom-written Ksplice patch will contain a bug that causes your kernel to crash - worst case would be if that crash happens after the kernel has been running for a while. I'm sure the people at Ksplice are much smarter than I am, but every time a security update for the kernel is released they will be stressing to release a Ksplice update to be able to provide value for their customers (the whole point of a subscription is so that you get the security update faster than planning a reboot takes). The way Ksplice works is that it, for each update, injects all changed functions into the kernel and replaces the old functions with a jump to the new version of the same function. Even though it might not cause what you would consider a production-threatening memory leak, I would still like to clear out the old code from memory every once in a while.
  - pbhjpbhj 17y ago
    Thanks for the elucidation. So, the reboot is required because the patches cause the old code to remain but simply be long-jumped past to the injected new version of that block of instructions. Got it. I'm not sure I'm in with you on Ksplice having to be really fast. The benefit is virtually no downtime but people are still going to test the patches on their testing servers and thus will still be testing in the wild before implementing fully.

by mmelin 17y ago

pbhjpbhj 17y ago

>wait until a botched patch causes systems worldwide to crash and burn I'm not following you here. Why does reboot-less updating of the kernel mean that the patches won't be tested. Also what DoS attack were you thinking of? Lastly, clean up memory? The top uptimes on Netcraft are >1000 days, is this necessary, are there specific memory leaks you're considering?

mmelin 17y ago
Using Ksplice means that you're letting a private company inject custom code directly into your running kernel. The paper explains that most Linux security updates are applied without modification, but some updates require Ksplice to write custom code for the patches to work (specifically if the update changes any data structures). My pessimistic side says that sooner or later this custom-written Ksplice patch will contain a bug that causes your kernel to crash - worst case would be if that crash happens after the kernel has been running for a while. I'm sure the people at Ksplice are much smarter than I am, but every time a security update for the kernel is released they will be stressing to release a Ksplice update to be able to provide value for their customers (the whole point of a subscription is so that you get the security update faster than planning a reboot takes). The way Ksplice works is that it, for each update, injects all changed functions into the kernel and replaces the old functions with a jump to the new version of the same function. Even though it might not cause what you would consider a production-threatening memory leak, I would still like to clear out the old code from memory every once in a while.
- pbhjpbhj 17y ago
  Thanks for the elucidation. So, the reboot is required because the patches cause the old code to remain but simply be long-jumped past to the injected new version of that block of instructions. Got it. I'm not sure I'm in with you on Ksplice having to be really fast. The benefit is virtually no downtime but people are still going to test the patches on their testing servers and thus will still be testing in the wild before implementing fully.