From: Paul Moore <paul@xxxxxxxxxxxxxx> Date: Wed, 21 Aug 2019 23:27:03 -0400 > On Wed, Aug 21, 2019 at 6:50 PM David Miller <davem@xxxxxxxxxxxxx> wrote: >> From: Paul Moore <paul@xxxxxxxxxxxxxx> >> Date: Wed, 21 Aug 2019 18:00:09 -0400 >> >> > I was just made aware of the skb extension work, and it looks very >> > appealing from a LSM perspective. As some of you probably remember, >> > we (the LSM folks) have wanted a proper security blob in the skb for >> > quite some time, but netdev has been resistant to this idea thus far. >> > >> > If I were to propose a patchset to add a SKB_EXT_SECURITY skb >> > extension (a single extension ID to be shared among the different >> > LSMs), would that be something that netdev would consider merging, or >> > is there still a philosophical objection to things like this? >> >> Unlike it's main intended user (MPTCP), it sounds like LSM's would use >> this in a way such that it would be enabled on most systems all the >> time. >> >> That really defeats the whole purpose of making it dynamic. :-/ > > I would be okay with only adding a skb extension when we needed it, > which I'm currently thinking would only be when we had labeled > networking actually configured at runtime and not just built into the > kernel. In SELinux we do something similar today when it comes to our > per-packet access controls; if labeled networking is not configured we > bail out of the LSM hooks early to improve performance (we would just > be comparing unlabeled_t to unlabeled_t anyway). I think the other > LSMs would be okay with this usage as well. > > While a number of distros due enable some form of LSM and the labeled > networking bits at build time, vary few (if any?) provide a default > configuration so I would expect no additional overhead in the common > case. > > Would that be acceptable? I honestly don't know, I kinda feared that once the SKB extension went in people would start dumping things there and that's exactly what's happening. I just so happened to be reviewing: https://patchwork.ozlabs.org/patch/1150091/ while you were writing this email. It's rediculous, the vultures are out.
