[uml-devel] Blank process command lines in 2.6.13.2?

[uml-devel] Blank process command lines in 2.6.13.2?

[Rob Landley]

Running a big script under UML, I noticed this at the end of ps:

19869 pts/1    D+     0:03 tmpdir/linux rootfstype=hostfs rw quiet mem=48M 
DIR=/
19873 pts/1    S+     0:00 tmpdir/linux rootfstype=hostfs rw quiet mem=48M 
DIR=/
19874 pts/1    T+     0:00
19968 pts/1    T+     0:00
19979 pts/1    T+     0:00
19981 pts/1    T+     0:04
19983 pts/2    R+     0:00 ps ax

*boggle*

This expected?

Rob


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Re: [uml-devel] Blank process command lines in 2.6.13.2?

[Jeff Dike]

On Sun, Oct 09, 2005 at 04:23:34PM -0500, Rob Landley wrote:
> 19874 pts/1    T+     0:00
> 19968 pts/1    T+     0:00
> 19979 pts/1    T+     0:00
> 19981 pts/1    T+     0:04
> 19983 pts/2    R+     0:00 ps ax
> 
> *boggle*
> 
> This expected?

Yeah, it's not unexpected.  The host tasks for UML processes inherit the
arglist address from UML, but UML has completely redone their address spaces,
so those addresses don't point at arguments any more.

				Jeff


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Re: [uml-devel] Blank process command lines in 2.6.13.2?

[Rob Landley]

On Sunday 09 October 2005 21:06, Jeff Dike wrote:
> On Sun, Oct 09, 2005 at 04:23:34PM -0500, Rob Landley wrote:
> > 19874 pts/1    T+     0:00
> > 19968 pts/1    T+     0:00
> > 19979 pts/1    T+     0:00
> > 19981 pts/1    T+     0:04
> > 19983 pts/2    R+     0:00 ps ax
> >
> > *boggle*
> >
> > This expected?
>
> Yeah, it's not unexpected.  The host tasks for UML processes inherit the
> arglist address from UML, but UML has completely redone their address
> spaces, so those addresses don't point at arguments any more.

Any likelihood that at some point in the future it could accidentally point to 
something it would be a bad idea to display?

Rob


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Re: [uml-devel] Blank process command lines in 2.6.13.2?

[Jeff Dike]

On Mon, Oct 10, 2005 at 12:10:10AM -0500, Rob Landley wrote:
> Any likelihood that at some point in the future it could accidentally point to 
> something it would be a bad idea to display?

I think the worst case is skas3 with no stack randomization, where that
page will point somewhere into the process stack.  There is some slight 
possibility that something could store a password on its stack, and have that
end up in the area that the host ps looks for arguments.  This would make the
password visible on the host for the time that this process in context.

With stack randomization, the UML process stacks will be located
elsewhere almost all the time, so with skas3, there is a smaller
chance that there will be a visible password there.

With skas0, that page is the stub signal stack, which contains no sensitive
information.

				Jeff


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Re: [uml-devel] Blank process command lines in 2.6.13.2?

[Rob Landley]

On Monday 10 October 2005 09:36, Jeff Dike wrote:
> I think the worst case is skas3 with no stack randomization, where that
> page will point somewhere into the process stack.  There is some slight
> possibility that something could store a password on its stack, and have
> that end up in the area that the host ps looks for arguments.  This would
> make the password visible on the host for the time that this process in
> context.

I'm not so worried about sensitive info because in the parent kernel you can 
just attach to the process from a debugger (although not necessarily as a 
different, normal user).  I'm actually slightly more concerned about high 
ascii garbage or who knows what showing up and making ps look really weird.

> With stack randomization, the UML process stacks will be located
> elsewhere almost all the time, so with skas3, there is a smaller
> chance that there will be a visible password there.
>
> With skas0, that page is the stub signal stack, which contains no sensitive
> information.

Is there any way to move the stub signal stack on skas0 by one page so that we 
can still have ps on the parent system look right?  I don't know how hard 
that is.  (Is there a design document for -skas0 anywhere?  I found 
the /dev/anon page...)

Rob


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