From mboxrd@z Thu Jan 1 00:00:00 1970 From: Haggai Eran Subject: Re: CVE-2014-8159 kernel: infiniband: uverbs: unprotected physical memory access Date: Fri, 3 Apr 2015 08:39:44 +0000 Message-ID: <1428050408201.35668@mellanox.com> References: <1427969085.17020.5.camel@opteya.com> <1427981431.22575.21.camel@opteya.com> <551D5DC8.6070909@mellanox.com> <1427992506.22575.80.camel@opteya.com> ,<1428007208.22575.104.camel@opteya.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <1428007208.22575.104.camel-RlY5vtjFyJ3QT0dZR+AlfA@public.gmane.org> Content-Language: en-US Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Yann Droneaud , Shachar Raindel Cc: Sagi Grimberg , " (linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org)" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org On Thursday, April 2, 2015 11:40 PM, Yann Droneaud wrote: > Le jeudi 02 avril 2015 =E0 16:44 +0000, Shachar Raindel a =E9crit : >> > -----Original Message----- >> > From: Yann Droneaud [mailto:ydroneaud-RlY5vtjFyJ3QT0dZR+AlfA@public.gmane.org] >> > Sent: Thursday, April 02, 2015 7:35 PM >=20 >> > Another related question: as the large memory range could be regis= tered >> > by user space with ibv_reg_mr(pd, base, size, IB_ACCESS_ON_DEMAND)= , >> > what's prevent the kernel to map a file as the result of mmap(0, .= =2E.) >> > in this region, making it available remotely through IBV_WR_RDMA_= READ / >> > IBV_WR_RDMA_WRITE ? >> > >> >> This is not a bug. This is a feature. >> >> Exposing a file through RDMA, using ODP, can be done exactly like th= is. >> Given that the application explicitly requested this behavior, I don= 't >> see why it is a problem. >=20 > If the application cannot choose what will end up in the region it ha= s > registered, it's an issue ! >=20 > What might happen if one library in a program call mmap(0, size, ...)= to > load a file storing a secret (a private key), and that file ends up > being mapped in an registered but otherwise free region (afaict, the > kernel is allowed to do it) ? > What might happen if one library in a program call call mmap(0, > size, ..., MAP_ANONYMOUS,...) to allocate memory, call mlock(), then > write in this location a secret (a passphrase), and that area ends up > in the memory region registered for on demand paging ? >=20 > The application haven't choose to disclose these confidential piece o= f > information, but they are available for reading/writing by remote > through RDMA given it knows the rkey of the memory region (which is a > 32bits value). >=20 > I hope I'm missing something, because I'm not feeling confident such > behavor is a feature. What we are aiming for is the possibility to register the entire proces= s' address=20 space for RDMA operations (if the process chooses to use this feature). This is similar to multiple threads accessing the same address space. I= 'm sure=20 you wouldn't be complaining about the ability of one thread to access t= he secret=20 passphrase mmapped by another thread in your example. > I'm trying to understand how the application can choose what is expos= ed > through RDMA if it registers a very large memory region for later use > (but do not actually explicitly map something there yet): what's the > consequences ? >=20 > void *start =3D sbrk(0); > size_t size =3D ULONG_MAX - (unsigned long)start; >=20 > ibv_reg_mr(pd, start, size, IB_ACCESS_ON_DEMAND) The consequences are exactly as you wrote. Just as giving a non-ODP rke= y=20 to a remote node allows the node to access the registered memory behind= that=20 rkey, giving an ODP rkey to a remote node allows that node to access th= e=20 virtual address space behind that rkey. Regards, Haggai-- To unsubscribe from this list: send the line "unsubscribe linux-rdma" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html