Messages in this thread | | | Date | Mon, 1 Aug 2011 23:22:45 +0400 | From | Vasiliy Kulikov <> | Subject | Re: [kernel-hardening] Re: initcall dependency problem (ns vs. threads) |
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On Mon, Aug 01, 2011 at 12:07 -0700, Andrew Morton wrote: > On Mon, 1 Aug 2011 23:03:41 +0400 > Vasiliy Kulikov <segoon@openwall.com> wrote: > > > > Are we talking about init_ipc_ns.ids[] here? If so, did you try > > > initializing the three rwsems at compile-time? > > > > > > That's rather a nasty hack though. It'd be better to run the mystery > > > init function before starting the threads. > > > > Looks like it solves the race. > > What patch are you talking about here?
Sorry for short sentences :) I tried the patch you've suggested - initialize rw_mutex in the init_ipc_ns declaration. Surely, it solves a specific race. As no kernel threads actually use shm, other fields are not needed to be initialized before do_initcall().
However, it is a bit ugly as it divides namespace initialization code into init_ipc_ns initialization and other namespaces. It's better to use the same code for all namespaces (as it currently is).
> > However, I think it should be solved on > > another level. > > What level?
I mean it is a bug of _implicit_ assume that kthreads don't use ns related information. So, AFAICS, it can be fixed 2 ways:
1) Move creations of kernel threads somewhere after namespaces initializations in the init chain.
2) Deferring threads creation until all ns initialization is done.
> > Other bugs might be hidden with this race. > > What bugs?
I don't speak about specific bugs (I know the only one, which is this shm related bug), but I suppose some threads might use some ns related information as well. At least I don't see whether it is somehow explicitly denied currently.
Thanks,
-- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments
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