James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> writes: > On Fri, 2017-02-17 at 14:57 +1300, Eric W. Biederman wrote: >> I think I am missing something but I completely do not understand >> that subthread that says use file marks and perform the work in the >> vfs. The problem is that fundamentally we need multiple mappings and >> I don't see a mark on a file (even an inherited mark) providing the >> mapping so I don't see the point. > > The point of the mark is that it's a statement by the system > administrator that the underlying subtree is safe to be mounted by an > unprivileged container in the containers user view (i.e. with > current_user_ns() == s_user_ns). For the unprivileged container > there's no real arbitrary s_user_ns use case because the unprivileged > container must prove it can set up the mapping, so it would likely > always be mounting from within a user_ns with the mapping it wanted. As a statement that it is ok for the unprivileged mapping code to operate that seems reasonable. I don't currently the need for such an ok from the system adminstrator, but if you need it a flag that propagates to children and child directories seems reasonable. Eric
