> -----Original Message----- > From: Hiroshi Shimamoto [mailto:h-shimam...@ct.jp.nec.com] > Sent: Wednesday, January 21, 2015 4:18 AM > To: David Laight; Skidmore, Donald C; Bjørn Mork > Cc: e1000-devel@lists.sourceforge.net; net...@vger.kernel.org; Choi, Sy > Jong; linux-ker...@vger.kernel.org; Hayato Momma > Subject: RE: [E1000-devel] [PATCH 1/2] if_link: Add VF multicast promiscuous > mode control > > > Subject: RE: [E1000-devel] [PATCH 1/2] if_link: Add VF multicast > > promiscuous mode control > > > > From: Hiroshi Shimamoto > > > My concern is what is the real issue that VF multicast promiscuous mode > can cause. > > > I think there is the 4k entries to filter multicast address, and the > > > current ixgbe/ixgbevf can turn all bits on from VM. That is almost same as > enabling multicast promiscuous mode. > > > I mean that we can receive all multicast addresses by an onerous > operation in untrusted VM. > > > I think we should clarify what is real security issue in this context. > > > > If you are worried about passing un-enabled multicasts to users then > > what about doing a software hash of received multicasts and checking > > against an actual list of multicasts enabled for that hash entry. > > Under normal conditions there is likely to be only a single address to > > check. > > > > It may (or may not) be best to use the same hash as any hashing > > hardware filter uses. > > thanks for the comment. But I don't think that is the point. > > I guess, introducing VF multicast promiscuous mode seems to add new > privilege to peek every multicast packet in VM and that doesn't look good. > On the other hand, I think that there has been the same privilege in the > current ixgbe/ixgbevf implementation already. Or I'm reading the code > wrongly. > I'd like to clarify what is the issue of allowing to receive all multicast > packets.
Allowing a VM to give itself the privilege of seeing every multicast packet could be seen as a hole in VM isolation. Now if the host system allows this policy I don't see this as an issue as someone specifically allowed this to happen and then must not be concerned. We could even log that it has occurred, which I believe your patch did do. The issue is also further muddied, as you mentioned above, since some of these multicast packets are leaking anyway (the HW currently uses a 12 bit mask). It's just that this change would greatly enlarge that hole from a fraction to all multicast packets. > > thanks, > Hiroshi ------------------------------------------------------------------------------ New Year. New Location. New Benefits. New Data Center in Ashburn, VA. GigeNET is offering a free month of service with a new server in Ashburn. Choose from 2 high performing configs, both with 100TB of bandwidth. Higher redundancy.Lower latency.Increased capacity.Completely compliant. http://p.sf.net/sfu/gigenet _______________________________________________ E1000-devel mailing list E1000-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/e1000-devel To learn more about Intel® Ethernet, visit http://communities.intel.com/community/wired
