Re: [PATCH] audit: set TIF_AUDIT_SYSCALL only if audit filter has been populated

> On Mar 8, 2018, at 1:12 AM, Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > >> On 2018-03-07 18:43, Paul Moore wrote: >>> On Wed, Mar 7, 2018 at 6:41 PM, Paul Moore <paul(a)paul-moore.com&gt; wrote: >>>> On Wed, Mar 7, 2018 at 11:48 AM, Jiri Kosina <jikos(a)kernel.org&gt; 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.

>> Link to the patch is below. >> >> * https://marc.info/?t=152041887600003&r=1&w=2 >> >> paul moore > > - RGB