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

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Date:	Wed, 12 Mar 2008 16:36:51 +0300
From:	Pavel Emelyanov <xemul@...nvz.org>
To:	"Serge E. Hallyn" <serue@...ibm.com>
CC:	Greg KH <greg@...ah.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,
	Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: [PATCH 5/9] Make use of permissions, returned by kobj_lookup

Serge E. Hallyn wrote:
> 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?  :)

No exactly. Look at security_ptrace, security_task_kill or 
security_vm_enough_memory for !SECURITY cases. I wanted to see similar 
for device access list not to replace selinux with this small "security
module" and not to carry this huge LSM for our modest purposes.

> 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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