Re: [PATCH 5/9] Make use of permissions, returned by kobj_lookup

Serge E. Hallyn
2008-03-12T13:09:30Z

Quoting Pavel Emelyanov (xemul@openvz.org):
> Greg KH wrote:
> > On Tue, Mar 11, 2008 at 12:57:55PM +0300, Pavel Emelyanov wrote:
> >> Besides, I've measured some things - the lat_syscall test for open from
> >> lmbench test suite and the nptl perf test. Here are the results:
> >>
> >> sec nosec
> >> open 3.0980s 3.0709s
> >> nptl 2.7746s 2.7710s
> >>
> >> So we have 0.88% loss in open and ~0.15% with nptl. I know, this is not that
> >> much, but it is noticeable. Besides, this is only two tests, digging deeper
> >> may reveal more.
> >
> > I think that is in the noise of sampling if you run that test many more
> > times.
>
> These numbers are average values of 20 runs of each test. I didn't
> provide the measurement accuracy, but the abs(open.sec - open.nosec)
> is greater than it.
>
> >> Let alone the fact that simply turning the CONFIG_SECURITY to 'y' puts +8Kb
> >> to the vmlinux...
> >>
> >> I think, I finally agree with you and Al Viro, that the kobj mapper is
> >> not the right place to put the filtering, but taking the above numbers
> >> into account, can we put the "hooks" into the #else /* CONFIG_SECURITY */
> >> versions of security_inode_permission/security_file_permission/etc?
> >
> > Ask the security module interface maintainers about this, not me :)
>
> OK :) Thanks for your time, Greg.
>
> So, Serge, since you already have a LSM-based version, maybe you can
> change it with the proposed "fix" and send it to LSM maintainers for
> review?

To take the point of view of someone who neither wants containers nor
LSM but just a fast box,

you're asking me to introduce LSM hooks for the !SECURITY case? :)

I can give it a shot, but I expect some complaints. Now at least the
_mknod hook shouldn't be a hotpath, and I suppose I can add yet
an #ifdef inside the !SECURITY version of security_inode_permission().
I still expect some complaints though. I'll send something soon.

thanks,
-serge

> > good luck,
> >
> > greg k-h
> >