On 7/25/2021 9:25 AM, Florian Westphal wrote:

Paul Moore [off-list ref] wrote:

quoted

quoted

There is the skb extension infra, does that work for you?

I was hopeful that when the skb_ext capability was introduced we might
be able to use it for the LSM(s), but when I asked netdev if they
would be willing to accept patches to leverage the skb_ext
infrastructure I was told "no".

I found

https://lore.kernel.org/netdev/CAHC9VhSz1_KA1tCJtNjwK26BOkGhKGbPT7v1O82mWPduvWwd4A@mail.gmail.com/#r (local)

and from what I gather from your comments and that of Casey
I think skb extensions is the correct thing for this (i.e., needs
netlabel/secid config/enablement so typically won't be active on
a distro kernel by default).

RedHat and android use SELinux and will want this. Ubuntu doesn't
yet, but netfilter in in the AppArmor task list. Tizen definitely
uses it with Smack. The notion that security modules are only used
in fringe cases is antiquated. 

It certainly makes more sense to me than doing lookups
in a hashtable based on a ID

Agreed. The data burden required to support a hash scheme
for the security module stacking case is staggering.

 (I tried to do that to get rid of skb->nf_bridge
pointer years ago and it I could not figure out how to invalidate an entry
without adding a new skb destructor callback).