Re: CVE-2014-8159 kernel: infiniband: uverbs: unprotected physical memory access

[Yann Droneaud]

Hi,

Le jeudi 02 avril 2015 Ã 10:52 +0000, Shachar Raindel a Ãcrit :
> > -----Original Message-----
> > From: Yann Droneaud [mailto:ydroneaud@xxxxxxxxxx]
> > Sent: Thursday, April 02, 2015 1:05 PM
> > Le mercredi 18 mars 2015 Ã 17:39 +0000, Shachar Raindel a Ãcrit :

> > > +	/*
> > > +	 * If the combination of the addr and size requested for this
> > memory
> > > +	 * region causes an integer overflow, return error.
> > > +	 */
> > > +	if ((PAGE_ALIGN(addr + size) <= size) ||
> > > +	    (PAGE_ALIGN(addr + size) <= addr))
> > > +		return ERR_PTR(-EINVAL);
> > > +
> > 
> > Can access_ok() be used here ?
> > 
> >          if (!access_ok(writable ? VERIFY_WRITE : VERIFY_READ,
> >                         addr, size))
> >                   return ERR_PTR(-EINVAL);
> > 
> 
> No, this will break the current ODP semantics.
> 
> ODP allows the user to register memory that is not accessible yet.
> This is a critical design feature, as it allows avoiding holding
> a registration cache. Adding this check will break the behavior,
> forcing memory to be all accessible when registering an ODP MR.
> 

Where's the check for the range being in userspace memory space,
especially for the ODP case ?

For non ODP case (eg. plain old behavior), does get_user_pages()
ensure the requested pages fit in userspace region on all 
architectures ? I think so.

In ODP case, I'm not sure such check is ever done ?
(Aside, does it take special mesure to protect shared mapping from
being read and/or *written* ?)

Regards.

-- 
Yann Droneaud
OPTEYA


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