Messages in this thread | | | From | Paul Moore <> | Date | Thu, 25 Aug 2022 15:19:09 -0400 | Subject | Re: [PATCH v5 0/4] Introduce security_create_user_ns() |
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On Thu, Aug 25, 2022 at 2:15 PM Eric W. Biederman <ebiederm@xmission.com> wrote: > Paul Moore <paul@paul-moore.com> writes: > > On Fri, Aug 19, 2022 at 10:45 AM Serge E. Hallyn <serge@hallyn.com> wrote: > >> I am hoping we can come up with > >> "something better" to address people's needs, make everyone happy, and > >> bring forth world peace. Which would stack just fine with what's here > >> for defense in depth. > >> > >> You may well not be interested in further work, and that's fine. I need > >> to set aside a few days to think on this. > > > > I'm happy to continue the discussion as long as it's constructive; I > > think we all are. My gut feeling is that Frederick's approach falls > > closest to the sweet spot of "workable without being overly offensive" > > (*cough*), but if you've got an additional approach in mind, or an > > alternative approach that solves the same use case problems, I think > > we'd all love to hear about it. > > I would love to actually hear the problems people are trying to solve so > that we can have a sensible conversation about the trade offs.
Here are several taken from the previous threads, it's surely not a complete list, but it should give you a good idea:
https://lore.kernel.org/linux-security-module/CAHC9VhQnPAsmjmKo-e84XDJ1wmaOFkTKPjjztsOa9Yrq+AeAQA@mail.gmail.com/
> As best I can tell without more information people want to use > the creation of a user namespace as a signal that the code is > attempting an exploit.
Some use cases are like that, there are several other use cases that go beyond this; see all of our previous discussions on this topic/patchset. As has been mentioned before, there are use cases that require improved observability, access control, or both.
> As such let me propose instead of returning an error code which will let > the exploit continue, have the security hook return a bool. With true > meaning the code can continue and on false it will trigger using SIGSYS > to terminate the program like seccomp does.
Having the kernel forcibly exit the process isn't something that most LSMs would likely want. I suppose we could modify the hook/caller so that *if* an LSM wanted to return SIGSYS the system would kill the process, but I would want that to be something in addition to returning an error code like LSMs normally do (e.g. EACCES).
-- paul-moore.com
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