Re: c/r: broken locking when executing map_files

[Vasiliy Kulikov]

On Mon, May 07, 2012 at 00:49 +0400, Cyrill Gorcunov wrote:
> On Mon, May 07, 2012 at 12:21:32AM +0400, Vasiliy Kulikov wrote:
> > On Sat, May 05, 2012 at 23:32 +0400, Cyrill Gorcunov wrote:
> > > On Sat, May 05, 2012 at 10:53:06PM +0400, Cyrill Gorcunov wrote:
> > >  | [root@neptune ~]# /proc/self/map_files/400000-419000
> > > 
> > > it sleeps forever until killed, which is not good I think. Vasiliy, could
> > > you remind me what exactly is problem if we use unlocked ptrace_may_access
> > > here?
> > 
> > There is a race between ptrace_may_access() and dname_to_vma_addr().
> > The target task may do exec() between these calls and
> > dname_to_vma_addr() will be called against a privileged task.  This may
> > lead to a leak of task maps.
> 
> Wait, the proc_map_files_lookup requires the caller to be cap-sysadmin
> granted, would not this be enough?

Yes :-) You can also remove additional checks after capable() in
readdir and revalidate functions.

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