On Thu, Aug 25, 2022 at 2:15 PM Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote: > Paul Moore <paul@xxxxxxxxxxxxxx> writes: > > On Fri, Aug 19, 2022 at 10:45 AM Serge E. Hallyn <serge@xxxxxxxxxx> 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@xxxxxxxxxxxxxx/ > 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
