Messages in this thread | | | Date | Thu, 8 Mar 2018 11:03:24 -0500 | From | Richard Guy Briggs <> | Subject | Re: [PATCH] audit: set TIF_AUDIT_SYSCALL only if audit filter has been populated |
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On 2018-03-08 06:30, Andy Lutomirski wrote: > > > > On Mar 8, 2018, at 1:12 AM, Richard Guy Briggs <rgb@redhat.com> wrote: > > > >> On 2018-03-07 18:43, Paul Moore wrote: > >>> On Wed, Mar 7, 2018 at 6:41 PM, Paul Moore <paul@paul-moore.com> wrote: > >>>> On Wed, Mar 7, 2018 at 11:48 AM, Jiri Kosina <jikos@kernel.org> wrote: > >>>>> On Wed, 7 Mar 2018, Andy Lutomirski wrote: > >>>>> Wow, this was a long time ago. > >>>> > >>>> Oh yeah; but it now resurfaced on our side, as we are of course receiving > >>>> a lot of requests with respect to making syscall performance great again > >>>> :) > >>> > >>> Ooof. I'm not sure I can handle making more things "great again" ;) > >>> > >>>>> From memory and a bit of email diving, there are two reasons. > >>>>> > >>>>> 1. The probably was partially solved (by Oleg, IIRC) by making auditctl > >>>>> -a task,never cause newly spawned tasks to not suck. Yes, it's a > >>>>> very partial solution. After considerable nagging, I got Fedora to > >>>>> default to -a task,never. > >>>> > >>>> Hm, right; that's a bit inconvenient, because it takes each and every > >>>> vendor having to realize this option, and put it in. Making kernel do the > >>>> right thing automatically sounds like a better option to me. > >>> > >>> This predates audit falling into my lap, but speaking generally I > >>> think it would be good if the kernel did The Right Thing, so long as > >>> it isn't too painful. > >>> > >>>>> 2. This patch, as is, may be a bit problematic. In particular, if one > >>>>> task changes the audit rules while another task is in the middle of > >>>>> the syscall, then it's too late to audit that syscall correctly. > >>>>> This could be seen as a bug or it could be seen as being just fine. > >>>> > >>>> I don't think this should be a problem, given the fact that the whole > >>>> timing/ordering is not predictable anyway due to scheduling. > >>>> > >>>> Paul, what do you think? > >>> > >>> I'm not overly concerned about the race condition between configuring > >>> the audit filters and syscalls that are currently in-flight; after all > >>> we have that now and "fixing" it would be pretty much impractical > >>> (impossible maybe?). Most serious audit users configure it during > >>> boot and let it run, frequent runtime changes are not common as far as > >>> I can tell. > > > > I'd agree the race condition here can't easily be fixed and isn't worth > > fixing for the reasons already stated (rules don't change often and may > > even be locked once in place relatively early, scheduling uncertainties). > > > >>> I just looked quickly at the patch and decided it isn't something I'm > >>> going to be able to carefully review in the time I've got left today, > >>> so it's going to have to wait until tomorrow and Friday ... however, > >>> speaking on general principle I don't have an objection to the ideas > >>> put forth here. > > > > The approach seems a bit draconian since it touches all tasks but only > > when adding the first rule or deleting the last. > > > > What we lose is the ability to set or clear individual task auditing and > > have it stick to speed up non-audited tasks when there are rules > > present, though this isn't currently used, in favour of audit_context > > presence. > > > >>> Andy, if you've got any Reviewed-by/Tested-by/NACK/etc. you want to > >>> add, that would be good to have. > >> > >> ... and I just realized that linux-audit isn't on the To/CC line, > >> adding them now. > > > > (and Andy's non-NACK missed too...) The mailing list *is* in MAINTAINERS. > > > > The mailing list bounces my emails.
They'll get approved.
> >> Link to the patch is below. > >> > >> * https://marc.info/?t=152041887600003&r=1&w=2 > >> > >> paul moore > > > > - RGB
- RGB
-- Richard Guy Briggs <rgb@redhat.com> Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada IRC: rgb, SunRaycer Voice: +1.647.777.2635, Internal: (81) 32635
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