Re: [patch 2/2] fs, proc: Introduce the /proc/<pid>/map_files/directory v6

[Vasiliy Kulikov]

Hi Tejun,

On Wed, Sep 07, 2011 at 01:51 +0900, Tejun Heo wrote:
> On Tue, Sep 06, 2011 at 02:15:18PM +0400, Vasiliy Kulikov wrote:
> >   c) If dentry is lazily dropped on each access attempt (or each illegal
> >      access) then PID2 can:
> > 
> >      i) read dentry line of /proc/slabinfo
> >      ii) call link(2) against /proc/PID/fd, which invalidates the
> >          specific dentry
> >      iii) re-read dentry line of /proc/slabinfo.  If it has decreased by
> >          one, the dentry existed before (ii).
> 
> If we really worry about this, probably the right thing to do is
> hiding slabinfo from mortal UIDs instead of worrying about what
> exactly are freed or not from each user.

I agree with you.  I don't think that showing system-global debug
information to all users by default is the right thing.  But some people
doesn't agree with this point of view:

http://thread.gmane.org/gmane.linux.kernel/1108378

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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