[PATCH v3 1/3] nsproxy: add struct nsset

[Christian Brauner]

On Mon, May 04, 2020 at 11:15:54AM -0500, Eric W. Biederman wrote:
> Christian Brauner <christian.brauner at ubuntu.com> writes:
> 
> > Add a simple struct nsset. It holds all necessary pieces to switch to a new
> > set of namespaces without leaving a task in a half-switched state which we
> > will make use of in the next patch. This patch simply switches the existing
> > setns logic over without causing a change in setns() behavior. This brings
> > setns() closer to how unshare() works(). The prepare_ns() function is
> > responsible to prepare all necessary information. This has two reasons.
> > First it minimizes dependencies between individual namespaces, i.e. all
> > install handler can expect that all fields are properly initialized
> > independent in what order they are called in. Second, this makes the code
> > easier to maintain and easier to follow if it needs to be changed.
> 
> This is buggy.
> 
> Your code assume that nstype == 0 is invalid.

Yep, good catch! That's a bug from rearranging the patches.

> 
> Passing nstype == 0 means don't verify the kind of file descriptor
> passed.
> 
> Quite frankly doing nstype & CLONE_XYZ is wrong.  It always
> needs to be nstype == CLONE_XYZ.

I mean, I can do the nstype == CLONE_NEW* in the preparatory patch and
then switch to flags & CLONE_NEW* later.

Let me fix this right now.

Christian