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

[Shachar Raindel]

Hi,

> -----Original Message-----
> From: Yann Droneaud [mailto:ydroneaud@xxxxxxxxxx]
> Sent: Thursday, April 02, 2015 1:05 PM
> To: Shachar Raindel
> Cc: oss-security@xxxxxxxxxxxxxxxxxx; <linux-rdma@xxxxxxxxxxxxxxx>
> (linux-rdma@xxxxxxxxxxxxxxx); linux-kernel@xxxxxxxxxxxxxxx;
> stable@xxxxxxxxxxxxxxx
> Subject: Re: CVE-2014-8159 kernel: infiniband: uverbs: unprotected
> physical memory access
> 
> Hi,
> 
> Le mercredi 18 mars 2015 Ã 17:39 +0000, Shachar Raindel a Ãcrit :
> > Hi,
> >

<snipped long e-mail>
 
> > +	/*
> > +	 * 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.

Thanks,
--Shachar