Can I move a kernel thread into a special mount namespace

Can I move a kernel thread into a special mount namespace

[Mark]

Hi,

Our requirement is, a user process sends a command to a kernel (3.10)
module, and the kernel module creates a kernel thread, which has to be
in same mount space with the user process since they have to access a
same path, which is not mounted in root namespace. But seems all kernel
threads have one parent "threadd", which is in root name space.

My question is, can I create a kernel thread with a special mount
space(e.g, same with "current"), or move it after it is created? I have
checked the setns syscall kernel source but still have no idea. I also
have posted this question in stackoverflow but got no answer:
 
http://stackoverflow.com/questions/39869545/can-i-move-a-kernel-thread-from-one-namespace-to-another

Thank you very much.

Re: Can I move a kernel thread into a special mount namespace

[Greg KH]

On Sun, Oct 16, 2016 at 07:18:43PM +0800, Mark wrote:
> Hi,
> 
> Our requirement is, a user process sends a command to a kernel (3.10)
> module, and the kernel module creates a kernel thread, which has to be
> in same mount space with the user process since they have to access a
> same path, which is not mounted in root namespace. But seems all kernel
> threads have one parent "threadd", which is in root name space.

Very odd requirement, do you have a pointer to your code anywhere?  What
exactly will that kernel thread do?

And why use such an obsolete and old kernel version?

thanks,

greg k-h

Re: Can I move a kernel thread into a special mount namespace

[Mark]

On 2016/10/26 20:31, Greg KH Wrote:
> On Sun, Oct 16, 2016 at 07:18:43PM +0800, Mark wrote:
>> Hi,
>>
>> Our requirement is, a user process sends a command to a kernel (3.10)
>> module, and the kernel module creates a kernel thread, which has to be
>> in same mount space with the user process since they have to access a
>> same path, which is not mounted in root namespace. But seems all kernel
>> threads have one parent "threadd", which is in root name space.
>
> Very odd requirement, do you have a pointer to your code anywhere?  What
> exactly will that kernel thread do?
>
> And why use such an obsolete and old kernel version?
>
> thanks,
>
> greg k-h
>

The kernel thread checks a file and if it exists then do something, but
the file is created in a separate namespace. Is this an odd requirement?
I cannot post the code. It's on an android release so kernel is 3.10. Is
there a solution on a newer kernel release?

Thank you very much, and sorry for late response:)

Re: Can I move a kernel thread into a special mount namespace

[Greg KH]

On Sun, Nov 13, 2016 at 04:50:09PM +0800, Mark wrote:
> 
> 
> On 2016/10/26 20:31, Greg KH Wrote:
> > On Sun, Oct 16, 2016 at 07:18:43PM +0800, Mark wrote:
> > > Hi,
> > > 
> > > Our requirement is, a user process sends a command to a kernel (3.10)
> > > module, and the kernel module creates a kernel thread, which has to be
> > > in same mount space with the user process since they have to access a
> > > same path, which is not mounted in root namespace. But seems all kernel
> > > threads have one parent "threadd", which is in root name space.
> > 
> > Very odd requirement, do you have a pointer to your code anywhere?  What
> > exactly will that kernel thread do?
> > 
> > And why use such an obsolete and old kernel version?
> > 
> > thanks,
> > 
> > greg k-h
> > 
> 
> The kernel thread checks a file and if it exists then do something, but
> the file is created in a separate namespace. Is this an odd requirement?

Yes, why should the kernel care about a file, the kernel should never be
reading files directly from userspace.

> I cannot post the code.

Why not?  You have our code, why can't you post yours?  :)

> It's on an android release so kernel is 3.10. Is there a solution on a
> newer kernel release?

I don't understand the problem you are trying to solve, can you perhaps
explain the issue, not the potential solution you are trying to use?
That would make it easier to understand.

thanks,

greg k-h