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    SubjectRe: [PATCH 5/9] Make use of permissions, returned by kobj_lookup
    Quoting Stephen Smalley (sds@tycho.nsa.gov):
    >
    > On Wed, 2008-03-12 at 08:09 -0500, Serge E. Hallyn wrote:
    > > 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.
    >
    > Not sure I'm following the plot here, but please don't do anything that
    > will prohibit the use of containers/namespaces with security modules
    > like SELinux/Smack.

    Absolutely not. There would be a redundant explicit hook in the
    !SECURITY case, but in the SECURITY=y case the regular hooks would be
    used by the device controller.

    I definately consider SELinux/Smack+containers an important case.

    > Yes, that's a legitimate use case, and there will
    > be people who will want to do that - they serve different but
    > complementary purposes (containers are _not_ a substitute for MAC). We
    > don't want them to be exclusive of one another.

    Agreed.

    -serge


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