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

[Shachar Raindel <raindel () mellanox com>]

Hi,

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