Re: c/r: broken locking when executing map_files
From: Vasiliy Kulikov
Date: Fri May 11 2012 - 13:57:51 EST
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.
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