RE: kprobes on by default in 2.6.20.1 kernel.org kernels

["Keshavamurthy, Anil S" <anil dot s dot keshavamurthy at intel dot com>]

 Good call. Never thought about this. Just checked the code and found
that we are 
doing the right thing i.e no probes are allowed on this code path :)

Anyway our goal is to make Kprobes production worthy and any feedback 
from the real world environment are very welcome and highly appreciated.


Thanks,
Anil  Keshavamurthy

-----Original Message-----
From: Nathan DeBardeleben [mailto:ndebard@lanl.gov] 
Sent: Thursday, March 01, 2007 4:10 PM
To: Keshavamurthy, Anil S
Cc: systemtap@sources.redhat.com
Subject: Re: kprobes on by default in 2.6.20.1 kernel.org kernels

I wasn't aware of that one.  However, since one is dynamically editing 
the kernel couldn't one probe the function that prints this out and 
claim there were no probes, even though you had some nice and nasty 
probes inserted?  Or have you guys declared that code as unprobable or 
something like that?

-- Nathan
Correspondence
---------------------------------------------------------------------
Nathan DeBardeleben, Ph.D.
Los Alamos National Laboratory
Parallel Tools Team
High Performance Computing Environments (HPC-4)
phone: 505-667-3428
email: ndebard@lanl.gov
---------------------------------------------------------------------



Keshavamurthy, Anil S wrote:
> Ha..If that is you concern, then I think you are lucky. We recently
> addressed this issues where 
> in one can list all the active probes in the system by accessing the
> file /sys/kernel/debug/kprobes/list. 
>
> And the output look like this
> =====================
> llm40:~/a # cat /sys/kernel/debug/kprobes/list
> c0169ae3  r  sys_read+0x0
> c0169ae3  k  sys_read+0x0
> c01694c8  k  vfs_write+0x0
> c0167d20  r  sys_open+0x0
> f8e658a6  k  reiserfs_delete_inode+0x0  reiserfs
> c0120f4a  k  do_fork+0x0
> c0120f4a  j  do_fork+0x0
> c0169b4a  r  sys_write+0x0
> c0169b4a  k  sys_write+0x0
> c0169622  r  vfs_read+0x0
> ====================
>
> Will this help?
>
> Thanks,
>
> -Anil Keshavamurthy
> Open Source Technology Center/SSG
> Intel Corp.
> (w) 503-712-4476
> email: anil.s.keshavamurthy@intel.com
>
> -----Original Message-----
> From: Nathan DeBardeleben [mailto:ndebard@lanl.gov] 
> Sent: Thursday, March 01, 2007 3:56 PM
> To: Keshavamurthy, Anil S
> Cc: systemtap@sources.redhat.com
> Subject: Re: kprobes on by default in 2.6.20.1 kernel.org kernels
>
> You know, it's not really me that has a problem with it.  I subscribe
to
>
> the camp of: If it requires root to run a probe, then someone who has 
> root can already do some pretty nefarious things to your system.  
> However, due the fact that with kprobes you can slip in a probe, and 
> then even hide that probe from being reported, I think some people I 
> work with are scared that it leaves them slightly more exposed /
> vulnerable.
>
> I'd love to be able to convince them to let me run probes on
production 
> systems but at this time they're relegated to test machines.  Honestly

> I'd like to be able to add to my repertoire a good argument to allow 
> kprobes on by default on these machines but when you're dealing with 
> security plans and documents and whatnot a new technology like this is

> easily deemed scary, unknown, and just relegated to the "security
risk" 
> column.
>
> -- Nathan
> Correspondence
> ---------------------------------------------------------------------
> Nathan DeBardeleben, Ph.D.
> Los Alamos National Laboratory
> Parallel Tools Team
> High Performance Computing Environments (HPC-4)
> phone: 505-667-3428
> email: ndebard@lanl.gov
> ---------------------------------------------------------------------
>
>
>
> Keshavamurthy, Anil S wrote:
>   
>> On Wed, Feb 28, 2007 at 04:24:14PM -0700, Nathan DeBardeleben wrote:
>>   
>>     
>>> I just wanted to probe (har har) to see if you guys knew why kprobes
>>>       
> is 
>   
>>> set to "Y" (in the kernel) by default on the latest 2.6.20.1 kernel
I
>>>       
>
>   
>>> got from kernel.org.  I don't consider this a great move and am a
>>>       
> little 
>   
>>> worried about it.  For one thing, I know now we'll actively make
>>>       
> certain 
>   
>>> it's off in all future kernels we build that are intended for
>>>       
> production 
>   
>>> machines.
>>>     
>>>       
>> Can you please explain your cause for worry in detail. In what way it

>> is causing problems. Hopefully we can address your concerns.
>>
>>   
>>     
>>> I grabbed the latest kernel to do some kprobes testing, went to 
>>> configure it to turn probing on and was very surprised to find it on
>>>       
> by 
>   
>>> default.
>>>     
>>>       
>> As a matter of fact, KPROBE is enabled by several major OSD like
>> Red Hat and SuSE on their enterprise versions and are in
>> the market since begining/middle of last year.
>>
>>   
>>     
>>> What's the process that the kernel maintainers go through to
>>>       
> determine 
>   
>>> which options are on by default anyway?
>>>     
>>>       
>> AFAIK, their is no formal process(depends on developer community). 
>> And if you are building a kernel for production machine then I assume

>> you just don;t depend on default config which can turn on lots of
>>     
> stuff 
>   
>> intended for testing and experimental purposes.
>>
>> -Anil Keshavamurthy
>>
>>   
>>     
>
>