linux-kernel - Re: [PATCH 5/9] Make use of permissions, returned by kobj

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Message-ID: <20080312130904.GB8308@sergelap.austin.ibm.com>
Date:	Wed, 12 Mar 2008 08:09:04 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Pavel Emelyanov <xemul@...nvz.org>
Cc:	Greg KH <greg@...ah.com>, serue@...ibm.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, menage@...gle.com,
	sukadev@...ibm.com, Al Viro <viro@...iv.linux.org.uk>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 5/9] Make use of permissions, returned by kobj_lookup

Quoting Pavel Emelyanov (xemul@...nvz.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
> > 
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