Re: kdbus: to merge or not to merge?

From: Andy Lutomirski
Date: Tue Jun 23 2015 - 20:53:12 EST

On Tue, Jun 23, 2015 at 4:19 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, Jun 22, 2015 at 11:06 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>> Can you opine as to whether you think that kdbus should be merged? I
>> don't mean whether you'd accept a pull request that Greg may or may
>> not send during this merge window -- I mean whether you think that
>> kdbus should be merged if it had appropriate review and people were
>> okay with the implementation.
> So I am still expecting to merge it, mainly for a rather simple
> reason: I trust my submaintainers, and Greg in particular. So when a
> major submaintainer wants to merge something, that pulls a *lot* of
> weight with me.

Then I'll try to review the parts that I can review, time permitting,
in the event that someone sends a clean, reviewable set of patches.
Preferably not during the merge window.

If my, or anyone else's, review uncovers an ABI issue, then I will be
correspondingly grumpy now that the userspace code is slated to ship
with new systemd versions. Because we can't actually ship a kernel that will fail to boot with Fedora Rawhide or Arch
AUR or whatever unless kdbus=0 is set on the kernel command line.

If someone ships an actual desktop sandbox based on kdbus custom
endpoints, I'll try to poke holes in it as usual. I don't intend to
review that part for security in advance because I've already said my
part: I think the design is unfit for its purpose. Given that I don't
see how one is supposed to use it in a sensible manner for sandboxing
in the first place, it's hard to evaluate whether it will do its job a

(NB: I think I may have figured out what people mean when they say
that custom endpoints are useful for sandboxes. They might be talking
about BusPolicy= in systemd .service files. That's a nifty feature,
but it seems rather limited and doesn't seem to me like it would be
useful for things like xdg-app. Also, it could certainly be
implemented in userspace.)


P.S. I still remain unconvinced that any of the other arguments for
merging it are better than the performance argument. But whatever.
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